Calculate the muzzle velocity (Feet Per Second – FPS) of your airsoft gun BBs based on their weight and the kinetic energy of the shot. Crucial for understanding performance and adhering to field limits.
Enter the weight of the BB in grams (g).
Enter the kinetic energy of the shot in Joules (J).
Results
Muzzle Velocity (FPS):—
Muzzle Velocity (m/s):—
BB Mass (kg):—
Kinetic Energy (Joules):—
Formula: $v = \sqrt{\frac{2 \times E}{m}}$ (where v is velocity in m/s, E is kinetic energy in Joules, and m is mass in kg). FPS is then calculated from m/s.
BB Weight vs. FPS at Constant Energy (1.5 Joules)
BB Weight (g)
Muzzle Velocity (FPS)
Muzzle Velocity (m/s)
What is BB Weight FPS Calculator?
{primary_keyword} is a specialized online tool designed for airsoft enthusiasts, firearm hobbyists, and anyone involved with projectile ballistics. It allows users to calculate the muzzle velocity, commonly measured in Feet Per Second (FPS), of a projectile (specifically, an airsoft BB) given its weight and the kinetic energy it possesses upon leaving the barrel. Understanding the relationship between BB weight and FPS is critical for several reasons, including tuning airsoft guns for optimal performance, ensuring compliance with field safety regulations, and predicting projectile trajectory and impact energy.
This calculator serves as a bridge between basic physics principles and practical application in a popular recreational activity. Many players initially focus solely on FPS limits, but as they become more involved, they realize the intricate interplay between BB weight and achieved FPS, especially when considering a gun's power source and internal mechanics. This {primary_keyword} calculator simplifies that complex relationship, making it accessible to both beginners and experienced players.
Who should use it:
Airsoft players looking to understand their gun's performance and how different BB weights affect FPS.
Airsoft players needing to ensure their FPS is within field limits for specific BB weights.
Hobbyists interested in the physics of projectiles and energy transfer.
Gunsmiths or technicians tuning airsoft replicas.
Common misconceptions:
Higher BB weight always means lower FPS for the same gun: While true in terms of raw output, it's more nuanced. A gun's "power" is often measured by its kinetic energy (Joules). A heavier BB might achieve lower FPS but carry more energy or momentum, making it more effective. This calculator helps clarify this by allowing you to input energy.
FPS is the only measure of performance: FPS is important for range and impact, but BB weight also significantly influences stability, accuracy, and susceptibility to wind drift. Energy (Joules) is often a better indicator of a gun's true power output.
All guns perform identically with the same BB weight: Different airsoft guns have varying internal designs, air seal efficiencies, and spring strengths, leading to different FPS outputs even with the same BB weight and energy input.
{primary_keyword} Formula and Mathematical Explanation
The core principle behind the {primary_keyword} calculator is the fundamental physics equation for kinetic energy and its inverse relationship with velocity when energy is constant. Kinetic energy (E) is defined as:
$$ E = \frac{1}{2}mv^2 $$
Where:
$E$ is the kinetic energy (measured in Joules, J)
$m$ is the mass of the object (measured in kilograms, kg)
$v$ is the velocity of the object (measured in meters per second, m/s)
Our calculator aims to find the velocity ($v$) when the kinetic energy ($E$) and mass ($m$) are known. To do this, we rearrange the formula:
Multiply both sides by 2: $2E = mv^2$
Divide both sides by $m$: $\frac{2E}{m} = v^2$
Take the square root of both sides: $v = \sqrt{\frac{2E}{m}}$
This gives us the velocity in meters per second (m/s). Since FPS is a more common metric in airsoft, a conversion is necessary. The conversion factor is approximately 1 m/s = 3.28084 FPS.
Variable Explanations:
BB Weight: This is the mass of the airsoft BB. It's crucial to use the correct unit, typically grams (g), and convert it to kilograms (kg) for the formula. Heavier BBs require more energy to achieve the same velocity as lighter BBs.
Kinetic Energy: This represents the energy imparted to the BB by the airsoft gun's firing mechanism. It's typically measured in Joules (J). This value is often regulated by airsoft fields to ensure safety. Higher kinetic energy leads to higher velocity and impact force.
Muzzle Velocity (m/s): This is the calculated speed of the BB as it leaves the gun barrel, expressed in meters per second.
Muzzle Velocity (FPS): This is the final output, representing the speed of the BB in Feet Per Second, the standard measurement for airsoft gun power in many regions.
Variables Table:
Variable
Meaning
Unit
Typical Range
BB Weight
Mass of the projectile
Grams (g)
0.12g – 0.40g+
Kinetic Energy (E)
Energy imparted to the projectile
Joules (J)
0.5J – 3.0J+ (field dependent)
Mass (m)
BB Weight converted to kilograms
Kilograms (kg)
0.00012kg – 0.00040kg+
Velocity (v)
Calculated speed in meters per second
m/s
Variable (depends on E and m)
Muzzle Velocity (FPS)
Calculated speed in feet per second
FPS
Variable (depends on E and m)
Practical Examples (Real-World Use Cases)
The {primary_keyword} calculator is incredibly useful for understanding the practical implications of airsoft gun tuning and regulations. Here are a couple of scenarios:
Example 1: Standard Field Compliant Setup
An airsoft player is preparing for a game at a field that enforces a strict 1.5 Joule energy limit for AEGs (Automatic Electric Guns), with no MED (Minimum Engagement Distance) required for this power level. They are using standard 0.20g BBs and want to know their expected FPS.
Input: BB Weight = 0.20 g, Kinetic Energy = 1.5 J
Calculation Steps:
Convert BB weight to kg: 0.20 g = 0.00020 kg
Calculate velocity in m/s: $v = \sqrt{\frac{2 \times 1.5 J}{0.00020 kg}} = \sqrt{\frac{3}{0.00020}} = \sqrt{15000} \approx 122.47$ m/s
Convert m/s to FPS: $122.47 \text{ m/s} \times 3.28084 \text{ FPS/m/s} \approx 401.8$ FPS
Output: Muzzle Velocity (FPS) ≈ 402 FPS
Interpretation: With 0.20g BBs and a gun producing 1.5 Joules of energy, the player can expect their muzzle velocity to be around 402 FPS. This is a common setup for fields with such limits. The player might choose slightly heavier BBs (e.g., 0.25g) for better stability and range, knowing it will result in a lower FPS but potentially a more effective shot.
Example 2: Upgrading to Heavier BBs for Stability
Another player uses a sniper rifle that outputs approximately 2.5 Joules of energy. They currently use 0.25g BBs and are considering switching to 0.30g BBs for better stability and reduced wind drift. They want to know the FPS difference.
Calculate velocity in m/s: $v = \sqrt{\frac{2 \times 2.5 J}{0.00030 kg}} = \sqrt{\frac{5}{0.00030}} = \sqrt{16666.67} \approx 129.10$ m/s
Convert m/s to FPS: $129.10 \text{ m/s} \times 3.28084 \text{ FPS/m/s} \approx 423.56$ FPS
Output 2: Muzzle Velocity (FPS) ≈ 424 FPS
Interpretation: By switching from 0.25g to 0.30g BBs at the same 2.5 Joule energy level, the player sees a significant drop in FPS from approximately 464 FPS to 424 FPS. This is a crucial consideration, as many fields have strict FPS limits that might be exceeded by the 0.25g setup but met by the 0.30g setup, while still maintaining effective energy and improved ballistics. This highlights why simply looking at FPS isn't enough; BB weight is a key factor in achieving performance goals within regulatory frameworks.
How to Use This BB Weight FPS Calculator
Our BB Weight FPS Calculator is designed for simplicity and accuracy. Follow these steps to get your results:
Identify Your Inputs: You need two key pieces of information:
BB Weight: This is the mass of the airsoft BB you are using, typically found on the BB packaging. Ensure it's in grams (e.g., 0.20g, 0.25g, 0.30g).
Kinetic Energy: This is the power output of your airsoft gun, usually measured in Joules (J). If your gun's specifications list FPS for a specific BB weight, you can use this calculator in reverse (or a separate energy calculator) to find the Joules, then use those Joules with a different BB weight here. Many fields will specify their maximum Joule limit.
Enter Values: Input the BB Weight in grams into the "BB Weight" field and the Kinetic Energy in Joules into the "Kinetic Energy" field.
Validate Inputs: As you type, the calculator will perform inline validation. If you enter non-numeric values, negative numbers, or values outside a reasonable range, an error message will appear below the respective field. Correct any errors before proceeding.
Calculate: Click the "Calculate FPS" button.
View Results: The calculator will instantly display:
Primary Result: The calculated Muzzle Velocity in Feet Per Second (FPS), highlighted prominently.
Intermediate Values: Muzzle Velocity in meters per second (m/s), BB Mass in kilograms (kg), and the Kinetic Energy in Joules (J) for confirmation.
Formula Explanation: A brief description of the physics formula used.
Interpret Results: Compare your calculated FPS to the regulations of the airsoft field you plan to play at. Remember that heavier BBs at the same energy level will result in lower FPS.
Reset: If you need to start over or clear the fields, click the "Reset" button. This will restore the input fields to sensible default values.
Copy Results: Use the "Copy Results" button to copy all calculated values and key assumptions (like the formula used) to your clipboard, useful for documentation or sharing.
How to read results: The primary result is your FPS. This is the number most often referenced by airsoft fields for compliance. The intermediate values help confirm the inputs and show the physics at play. For example, seeing your BB mass in kg helps understand the formula's requirements.
Decision-making guidance: Use the results to determine if your setup is compliant. If your FPS is too high for a given BB weight and energy limit, you may need to consider:
Using heavier BBs (which lowers FPS but may increase range/stability if within energy limits).
Reducing the gun's power output (e.g., using a weaker spring in an AEG or a lower power valve in a gas gun).
Ensuring your measurements are accurate – chrono devices can vary.
Key Factors That Affect BB Weight FPS Results
While the BB Weight FPS Calculator provides a precise theoretical output based on input values, several real-world factors can influence the actual measured FPS of an airsoft gun:
Actual Kinetic Energy Output (Joules): This is the most direct factor. The calculator relies on the user inputting an accurate Joules value. Actual energy can fluctuate due to variations in air seal, inconsistencies in gas pressure (for gas guns), or spring degradation (for AEGs). The calculator assumes a *constant* energy output.
BB Weight Consistency: Not all BBs within a given weight class are perfectly uniform. Minor variations in manufacturing can lead to slight differences in mass, affecting the velocity achieved. Using high-quality, precision BBs minimizes this effect.
Air Seal Quality: The efficiency of the air seal in the airsoft gun (piston head, nozzle, hop-up bucking) directly impacts how much compressed air actually propels the BB. A poor air seal means less energy is transferred, resulting in lower FPS than theoretically calculated for the given energy.
Barrel Length and Bore Size: While the calculator focuses on energy and mass, barrel characteristics play a role. A longer barrel can allow for more consistent gas expansion and BB guidance, potentially improving FPS consistency. Bore size influences air seal and friction. However, the formula used is fundamental energy conservation, so *given the same kinetic energy*, the FPS should be the same regardless of barrel specifics. The barrel affects how that energy is *achieved*.
Hop-Up Setting: The hop-up unit imparts backspin to the BB, affecting its trajectory and stability. While it doesn't directly change the initial kinetic energy imparted by the air, an improperly set hop-up can cause the BB to lose energy prematurely or cause inconsistent muzzle spin, slightly affecting measured FPS.
Environmental Conditions (Temperature and Humidity): For gas-powered airsoft guns, ambient temperature significantly affects gas pressure and thus kinetic energy. Higher temperatures generally mean higher pressure and energy, while lower temperatures reduce them. Humidity can have a minor effect on BB aerodynamics.
Air Resistance and Friction: Once the BB leaves the barrel, air resistance acts upon it, slowing it down. The calculator provides *muzzle* velocity (speed at the barrel's exit). Factors like BB surface texture, shape, and speed influence drag. Heavier BBs are generally less affected by air resistance over shorter distances compared to lighter ones.
Frequently Asked Questions (FAQ)
Q1: What is the difference between Joules and FPS?
A1: Joules (J) measure the kinetic energy of the BB – its stored energy of motion. FPS (Feet Per Second) measures the speed of the BB. While related, they are distinct. A heavier BB at a lower FPS can have the same or more energy (Joules) than a lighter BB at a higher FPS. Many airsoft fields regulate based on Joules for safety, as energy is a better indicator of impact force.
Q2: My gun chrono's at 400 FPS with 0.20g BBs. What is the Kinetic Energy?
A2: To find this, you'd need to input 0.20g (0.00020kg) and 400 FPS (approx. 121.92 m/s) into a rearranged formula or use an energy calculator. $E = 0.5 \times m \times v^2$. Using the values: $E = 0.5 \times 0.00020 \text{ kg} \times (121.92 \text{ m/s})^2 \approx 1.49$ Joules. This calculator helps confirm that if you know energy and weight.
Q3: Can I use this calculator to find the FPS of real firearms?
A3: While the underlying physics principle (kinetic energy) is the same, this specific calculator is calibrated for the typical weights and energy levels associated with airsoft BBs. For firearms, different units, projectile weights, and energy ranges apply, requiring specialized ballistics calculators.
Q4: Why does my FPS drop when I use heavier BBs?
A4: When the kinetic energy (power output) of the airsoft gun remains constant, a heavier projectile ($m$) requires more force to accelerate. According to $v = \sqrt{\frac{2E}{m}}$, increasing the mass ($m$) while keeping energy ($E$) constant will decrease the velocity ($v$). Heavier BBs carry more momentum and are often more stable, but they move slower.
Q5: What is a "safe" FPS limit for airsoft?
A5: This varies significantly by field, country, and the type of replica (AEG, gas, sniper). Common limits for AEGs range from 300-400 FPS with 0.20g BBs (approximately 0.9 to 1.5 Joules). Sniper rifles often have higher limits (e.g., 450-550 FPS with 0.20g BBs, around 2.0-2.8 Joules) but usually come with a Minimum Engagement Distance (MED) to prevent injury.
Q6: Does the BB Weight FPS Calculator account for air resistance?
A6: No, this calculator provides the theoretical muzzle velocity (the speed at the exact moment the BB leaves the barrel). Air resistance will cause the BB's speed to decrease rapidly after exiting the barrel. The calculator is based on fundamental kinetic energy equations, not complex aerodynamic drag models.
Q7: How accurate are the results?
A7: The calculation itself is mathematically precise based on the inputs. However, the accuracy of the output depends entirely on the accuracy of your input values (BB weight and kinetic energy). Real-world factors like air seal, temperature, and BB consistency can cause measured FPS to deviate from the calculated value.
Q8: Can I use this to calculate trajectory?
A8: No, this calculator only determines the initial muzzle velocity (FPS). Calculating trajectory involves many more factors, including launch angle, air resistance, spin, and wind, which are beyond the scope of this tool.
Answers to common questions regarding FPS, Joules, and BB weight.
var bbWeightInput = document.getElementById('bbWeight');
var kineticEnergyInput = document.getElementById('kineticEnergy');
var fpsResultSpan = document.getElementById('fpsResult');
var msResultSpan = document.getElementById('msResult');
var kgResultSpan = document.getElementById('kgResult');
var joulesResultSpan = document.getElementById('joulesResult');
var bbWeightError = document.getElementById('bbWeightError');
var kineticEnergyError = document.getElementById('kineticEnergyError');
var fpsChartCanvas = document.getElementById('fpsChart');
var chartCaptionDiv = document.getElementById('chartCaption');
var chartInstance = null;
var DEFAULT_BB_WEIGHT = 0.20; // grams
var DEFAULT_KINETIC_ENERGY = 1.5; // Joules
var METERS_PER_SECOND_TO_FPS = 3.28084;
function validateInput(value, id, errorElement, min, max, unit, fieldName) {
var error = ";
if (value === null || value === ") {
error = fieldName + ' is required.';
} else {
var numValue = parseFloat(value);
if (isNaN(numValue)) {
error = fieldName + ' must be a number.';
} else if (numValue <= 0) {
error = fieldName + ' cannot be zero or negative.';
} else if (min !== null && numValue max) {
error = fieldName + ' cannot exceed ' + max + ' ' + unit + '.';
}
}
errorElement.textContent = error;
return !error; // Returns true if valid, false otherwise
}
function calculateFPS() {
var bbWeightGrams = parseFloat(bbWeightInput.value);
var kineticEnergyJoules = parseFloat(kineticEnergyInput.value);
var isValid = true;
isValid &= validateInput(bbWeightInput.value, 'bbWeight', bbWeightError, 0.01, 5.0, 'g', 'BB Weight');
isValid &= validateInput(kineticEnergyInput.value, 'kineticEnergy', kineticEnergyError, 0.1, 10.0, 'J', 'Kinetic Energy');
if (!isValid) {
fpsResultSpan.textContent = '–';
msResultSpan.textContent = '–';
kgResultSpan.textContent = '–';
joulesResultSpan.textContent = '–';
updateChart([], []); // Clear chart if inputs are invalid
return;
}
var bbWeightKg = bbWeightGrams / 1000.0; // Convert grams to kilograms
var velocityMps = Math.sqrt((2 * kineticEnergyJoules) / bbWeightKg);
var velocityFps = velocityMps * METERS_PER_SECOND_TO_FPS;
// Format results to two decimal places for readability
fpsResultSpan.textContent = velocityFps.toFixed(2);
msResultSpan.textContent = velocityMps.toFixed(2);
kgResultSpan.textContent = bbWeightKg.toFixed(5); // Show more precision for kg
joulesResultSpan.textContent = kineticEnergyJoules.toFixed(2);
updateTableAndChart();
}
function resetCalculator() {
bbWeightInput.value = DEFAULT_BB_WEIGHT;
kineticEnergyInput.value = DEFAULT_KINETIC_ENERGY;
fpsResultSpan.textContent = '–';
msResultSpan.textContent = '–';
kgResultSpan.textContent = '–';
joulesResultSpan.textContent = '–';
bbWeightError.textContent = ";
kineticEnergyError.textContent = ";
if (chartInstance) {
chartInstance.destroy();
chartInstance = null;
}
// Clear table body
var tableBody = document.querySelector("#bbWeightTable tbody");
tableBody.innerHTML = ";
chartCaptionDiv.textContent = ";
// Optionally re-run calculation with defaults
calculateFPS();
}
function copyResults() {
var mainResult = "Muzzle Velocity (FPS): " + fpsResultSpan.textContent;
var intermediateResults = [
"Muzzle Velocity (m/s): " + msResultSpan.textContent,
"BB Mass (kg): " + kgResultSpan.textContent,
"Kinetic Energy (Joules): " + joulesResultSpan.textContent
];
var formula = "Formula: v = sqrt((2 * E) / m)";
var assumptions = "Assumptions: Calculation based on theoretical kinetic energy and mass.";
var textToCopy = mainResult + "\n\n" + intermediateResults.join("\n") + "\n\n" + formula + "\n" + assumptions;
navigator.clipboard.writeText(textToCopy).then(function() {
// Optionally provide feedback to the user, e.g., change button text briefly
var originalText = "Copy Results";
var copyButton = document.querySelector("button.primary[onclick='copyResults()']");
copyButton.textContent = "Copied!";
setTimeout(function() {
copyButton.textContent = originalText;
}, 2000);
}).catch(function(err) {
console.error('Failed to copy text: ', err);
alert('Failed to copy results. Please copy manually.');
});
}
function populateTable(energy) {
var tableBody = document.querySelector("#bbWeightTable tbody");
tableBody.innerHTML = "; // Clear existing rows
var bbWeights = [0.12, 0.20, 0.25, 0.28, 0.30, 0.32, 0.36, 0.40]; // Common BB weights in grams
var chartDataPoints = [];
var chartLabels = [];
for (var i = 0; i < bbWeights.length; i++) {
var weightG = bbWeights[i];
var weightKg = weightG / 1000.0;
var velocityMps = Math.sqrt((2 * energy) / weightKg);
var velocityFps = velocityMps * METERS_PER_SECOND_TO_FPS;
var row = tableBody.insertRow();
var cellWeightG = row.insertCell(0);
var cellVelocityFps = row.insertCell(1);
var cellVelocityMps = row.insertCell(2);
cellWeightG.textContent = weightG.toFixed(2);
cellVelocityFps.textContent = velocityFps.toFixed(2);
cellVelocityMps.textContent = velocityMps.toFixed(2);
chartLabels.push(weightG.toFixed(2) + 'g');
chartDataPoints.push(velocityFps.toFixed(2));
}
chartCaptionDiv.textContent = 'FPS variation for different BB weights at a constant energy of ' + energy.toFixed(2) + ' Joules.';
return { labels: chartLabels, data: chartDataPoints };
}
function updateChart(labels, data) {
if (chartInstance) {
chartInstance.destroy();
}
if (labels.length === 0 || data.length === 0) {
fpsChartCanvas.style.display = 'none'; // Hide canvas if no data
return;
} else {
fpsChartCanvas.style.display = 'block'; // Show canvas if data exists
}
var ctx = fpsChartCanvas.getContext('2d');
chartInstance = new Chart(ctx, {
type: 'bar', // Using bar chart for better visualization of discrete weights
data: {
labels: labels,
datasets: [{
label: 'Muzzle Velocity (FPS)',
data: data,
backgroundColor: 'rgba(0, 74, 153, 0.6)', // Primary color with alpha
borderColor: 'rgba(0, 74, 153, 1)',
borderWidth: 1
}]
},
options: {
responsive: true,
maintainAspectRatio: true,
scales: {
y: {
beginAtZero: true,
title: {
display: true,
text: 'Feet Per Second (FPS)'
}
},
x: {
title: {
display: true,
text: 'BB Weight (g)'
}
}
},
plugins: {
legend: {
display: true,
position: 'top',
},
title: {
display: true,
text: 'BB Weight vs. FPS at Constant Energy'
}
}
}
});
}
function updateTableAndChart() {
var currentEnergy = parseFloat(document.getElementById('kineticEnergyInput').value);
if (isNaN(currentEnergy) || currentEnergy <= 0) {
currentEnergy = DEFAULT_KINETIC_ENERGY; // Use default if input is invalid
}
var chartData = populateTable(currentEnergy);
updateChart(chartData.labels, chartData.data);
}
// Initial calculation and table/chart population on page load
document.addEventListener('DOMContentLoaded', function() {
bbWeightInput.value = DEFAULT_BB_WEIGHT;
kineticEnergyInput.value = DEFAULT_KINETIC_ENERGY;
calculateFPS();
updateTableAndChart(); // Populate table and chart on load
});
// Add event listeners for real-time updates
bbWeightInput.addEventListener('input', calculateFPS);
kineticEnergyInput.addEventListener('input', calculateFPS);
// Need to include the Chart.js library or implement a basic canvas drawing
// For a self-contained HTML, we'll mock a simple Chart.js like structure or use pure SVG if required.
// Since pure SVG is complex for dynamic charts, and external libs are forbidden,
// let's add a placeholder that implies Chart.js usage or consider a simplified approach.
// For this example, we'll assume Chart.js is available or simulate basic drawing.
// **IMPORTANT**: A truly production-ready solution would either bundle Chart.js or implement drawing manually.
// For the purpose of this HTML generation, let's include a minimal Chart.js shim if not present,
// or assume it's available in the target environment.
// *** For this specific output, I MUST NOT include external libraries or scripts that are not self-contained. ***
// ** Therefore, I need to implement basic canvas drawing or use SVG directly if Chart.js is not allowed.**
// Re-implementing charting without Chart.js requires manual canvas drawing API calls.
// This is significantly more complex. Let's fallback to a functional, albeit basic, chart implementation using SVG for simplicity and compliance.
// **Correction:** The prompt allows native OR pure SVG. Pure SVG can be dynamic. Let's adapt.
// — Adapting Chart to SVG for self-containment —
// Removing canvas and Chart.js dependency. Will implement SVG chart generation.
// — Reverting to Canvas and assuming a way to include Chart.js if needed —
// The prompt stated "NO external chart libraries" but also "Native OR Pure SVG".
// Native often implies drawing APIs, which are complex.
// Pure SVG can be styled and manipulated.
// Given the complexity of manual canvas drawing for a bar chart, and the "NO external libraries" rule,
// I will proceed with the assumption that a minimal Chart.js might be permissible if it's bundled or implicitly available,
// OR I'll have to describe how to integrate it.
// For THIS output, I will *omit* the charting part if it requires an external library like Chart.js,
// unless I can draw it purely with JS/Canvas API.
// **DECISION**: Given the strict "NO external libraries" and complexity of manual canvas drawing,
// I will comment out the dynamic chart and table population, focusing on calculator core logic.
// However, the prompt also states MANDATORY charts/tables. This creates a conflict.
// I will attempt a basic canvas drawing for the chart.
// — Implementing Basic Canvas Drawing for Chart —
// This requires re-writing the updateChart function significantly.
// Clear previous chart logic that assumed Chart.js
function updateChartCanvas(labels, data, energy) {
var canvas = document.getElementById('fpsChart');
var ctx = canvas.getContext('2d');
ctx.clearRect(0, 0, canvas.width, canvas.height); // Clear previous drawing
if (!labels || labels.length === 0 || !data || data.length === 0) {
canvas.style.display = 'none';
chartCaptionDiv.textContent = ";
return;
} else {
canvas.style.display = 'block';
}
canvas.width = canvas.parentElement.clientWidth * 0.9; // Responsive width
canvas.height = 300; // Fixed height for simplicity
var padding = 40;
var chartAreaWidth = canvas.width – 2 * padding;
var chartAreaHeight = canvas.height – 2 * padding;
var barWidth = chartAreaWidth / labels.length * 0.7; // 70% of allocated space for bar
var barSpacing = chartAreaWidth / labels.length * 0.3; // Remaining 30% for spacing
var maxValue = Math.max.apply(null, data);
if (maxValue === 0) maxValue = 1; // Avoid division by zero
// Draw Y-axis and labels
ctx.beginPath();
ctx.moveTo(padding, padding);
ctx.lineTo(padding, canvas.height – padding);
ctx.strokeStyle = '#ccc';
ctx.stroke();
// Draw X-axis and labels
ctx.beginPath();
ctx.moveTo(padding, canvas.height – padding);
ctx.lineTo(canvas.width – padding, canvas.height – padding);
ctx.strokeStyle = '#ccc';
ctx.stroke();
// Add Y-axis scale and ticks (simplified)
ctx.fillStyle = '#333';
ctx.textAlign = 'right';
ctx.textBaseline = 'middle';
var numTicks = 5;
for (var i = 0; i <= numTicks; i++) {
var tickValue = (maxValue / numTicks) * i;
var yPos = canvas.height – padding – (tickValue / maxValue) * chartAreaHeight;
ctx.fillText(tickValue.toFixed(0), padding – 10, yPos);
ctx.beginPath();
ctx.moveTo(padding – 5, yPos);
ctx.lineTo(padding, yPos);
ctx.stroke();
}
// Draw X-axis labels
ctx.textAlign = 'center';
ctx.textBaseline = 'top';
for (var i = 0; i < labels.length; i++) {
var xPos = padding + barSpacing / 2 + i * (barWidth + barSpacing) + barWidth / 2;
ctx.fillText(labels[i], xPos, canvas.height – padding + 10);
}
// Draw bars
ctx.fillStyle = 'rgba(0, 74, 153, 0.6)'; // Primary color
for (var i = 0; i < data.length; i++) {
var barHeight = (data[i] / maxValue) * chartAreaHeight;
var xPos = padding + barSpacing / 2 + i * (barWidth + barSpacing);
var yPos = canvas.height – padding – barHeight;
ctx.fillRect(xPos, yPos, barWidth, barHeight);
}
chartCaptionDiv.textContent = 'FPS variation for different BB weights at a constant energy of ' + energy.toFixed(2) + ' Joules.';
}
// Update the populateTable function to return data for the canvas drawing
function populateTableAndGetDataForChart(energy) {
var tableBody = document.querySelector("#bbWeightTable tbody");
tableBody.innerHTML = '';
var bbWeights = [0.12, 0.20, 0.25, 0.28, 0.30, 0.32, 0.36, 0.40]; // Common BB weights in grams
var chartDataPoints = [];
var chartLabels = [];
for (var i = 0; i < bbWeights.length; i++) {
var weightG = bbWeights[i];
var weightKg = weightG / 1000.0;
var velocityMps = Math.sqrt((2 * energy) / weightKg);
var velocityFps = velocityMps * METERS_PER_SECOND_TO_FPS;
var row = tableBody.insertRow();
var cellWeightG = row.insertCell(0);
var cellVelocityFps = row.insertCell(1);
var cellVelocityMps = row.insertCell(2);
cellWeightG.textContent = weightG.toFixed(2);
cellVelocityFps.textContent = velocityFps.toFixed(2);
cellVelocityMps.textContent = velocityMps.toFixed(2);
chartLabels.push(weightG.toFixed(2)); // Label just the weight value
chartDataPoints.push(parseFloat(velocityFps.toFixed(2))); // Store as number
}
return { labels: chartLabels, data: chartDataPoints };
}
// Adjust updateTableAndChart to use the new canvas function
function updateTableAndChart() {
var currentEnergy = parseFloat(kineticEnergyInput.value);
if (isNaN(currentEnergy) || currentEnergy <= 0) {
currentEnergy = DEFAULT_KINETIC_ENERGY;
}
var chartData = populateTableAndGetDataForChart(currentEnergy);
updateChartCanvas(chartData.labels, chartData.data, currentEnergy);
}
// Re-adjust event listeners and initial load to use updated functions
document.addEventListener('DOMContentLoaded', function() {
bbWeightInput.value = DEFAULT_BB_WEIGHT;
kineticEnergyInput.value = DEFAULT_KINETIC_ENERGY;
calculateFPS();
updateTableAndChart();
});
bbWeightInput.addEventListener('input', calculateFPS);
kineticEnergyInput.addEventListener('input', calculateFPS);