Plastic Weight Calculation Formula & Calculator
Accurately determine the weight of plastic components for manufacturing, cost estimation, and material management. Use our tool to simplify the plastic weight calculation formula.
Plastic Weight Calculator
Weight = Volume × Density
Cuboid
Cylinder
Sphere
Rectangular Prism (like a sheet/plate)
Select the basic geometric shape of your plastic component.
Acrylonitrile Butadiene Styrene (ABS)
Polycarbonate (PC)
High-Density Polyethylene (HDPE)
Polypropylene (PP)
Polyvinyl Chloride (PVC)
Polystyrene (PS)
Polyethylene Terephthalate (PET)
Custom Density
Choose a common plastic or enter a custom density.
Enter the specific density for your custom material.
Calculation Results
–.– kg
Volume: –.– cm³
Density: –.– g/cm³
Material: N/A
Formula: Weight = Volume × Density
Results copied to clipboard!
Weight vs. Volume
Comparison of component weight based on varying volumes for selected plastics.
What is Plastic Weight Calculation?
Plastic weight calculation refers to the process of determining the mass of a plastic component or product. This is a fundamental aspect in various industries, particularly in manufacturing, product design, supply chain management, and cost analysis. Accurate weight estimation is crucial for several reasons: it directly impacts material costs, shipping expenses, structural integrity, and overall product performance. Understanding the plastic weight calculation formula allows businesses to forecast expenses, optimize designs for material efficiency, and ensure compliance with weight-related regulations.
Who Should Use Plastic Weight Calculations?
A wide range of professionals and industries benefit from accurate plastic weight calculations:
- Product Designers & Engineers: To optimize material usage, ensure structural soundness, and estimate manufacturing costs.
- Manufacturing & Production Managers: For inventory management, production planning, and cost control.
- Procurement & Supply Chain Specialists: To forecast raw material needs and manage logistics costs.
- Sales & Marketing Teams: To provide accurate product specifications and shipping estimates.
- Quality Control Inspectors: To verify that components meet specified weight tolerances.
- Students & Educators: For learning and teaching principles of material science and engineering.
Common Misconceptions about Plastic Weight
Several common misunderstandings exist regarding plastic weight:
- "All plastics are lightweight": While plastics are generally lighter than metals, their densities vary significantly. Some engineering plastics can be denser than aluminum.
- "Shape doesn't matter for weight": The volume a plastic occupies directly influences its weight, and shape determines volume.
- "Density is constant for a plastic type": While standard density values are used, factors like additives, fillers, and manufacturing processes can slightly alter the density of a specific plastic batch.
- "Weight is only about material cost": Shipping, handling, and structural requirements tied to weight significantly contribute to the total product cost.
Plastic Weight Calculation Formula and Mathematical Explanation
The core principle behind calculating the weight of any object, including plastic components, is the relationship between its volume, density, and mass (weight). The fundamental plastic weight calculation formula is straightforward:
The Formula:
Weight = Volume × Density
This formula is a direct application of the definition of density, which is mass per unit volume. To calculate the weight (which we often use interchangeably with mass in practical contexts), we rearrange the density formula (Density = Mass / Volume) to solve for Mass (Weight).
Step-by-Step Derivation & Variable Explanations:
- Determine the Volume (V): The first step is to calculate the geometric volume of the plastic component. This depends on the component's shape. For simple geometric shapes, standard formulas are used. For complex shapes, CAD software or methods like water displacement might be necessary. The units for volume must be consistent (e.g., cubic centimeters, cubic meters).
- Identify the Density (ρ): Density is a material property that describes how much mass is contained in a given volume. Different types of plastics have different densities. These values are typically provided by the plastic manufacturer or can be found in material property databases. Density is usually expressed in units like grams per cubic centimeter (g/cm³) or kilograms per cubic meter (kg/m³).
- Calculate the Weight (W): Once the volume and density are known, multiply them together. Ensure that the units are compatible to yield the desired unit for weight (e.g., grams or kilograms). If density is in g/cm³ and volume is in cm³, the resulting weight will be in grams. This often needs conversion to kilograms for practical industrial use.
Variables Table:
| Variable | Meaning | Unit (Common) | Typical Range (Approx.) |
|---|---|---|---|
| Volume (V) | The amount of 3D space occupied by the plastic component. | cm³ (cubic centimeters) | Varies widely based on component size. |
| Density (ρ) | Mass per unit volume of the plastic material. | g/cm³ (grams per cubic centimeter) | 0.85 (e.g., Polyethylene) to 2.5+ (e.g., filled polymers) |
| Weight (W) | The mass of the plastic component. | kg (kilograms) or g (grams) | Varies widely based on component size and material. |
Note on Units: Consistency is key. If Volume is in cm³ and Density is in g/cm³, the result is in grams. To convert grams to kilograms, divide by 1000.
Practical Examples (Real-World Use Cases)
Example 1: Calculating the Weight of a Plastic Enclosure
Scenario: An engineer needs to estimate the weight of a plastic enclosure for a new electronic device. The enclosure is shaped like a rectangular prism (a box).
Inputs:
- Shape: Rectangular Prism (Sheet)
- Length: 20 cm
- Width: 15 cm
- Thickness: 0.3 cm
- Plastic Type: Polycarbonate (PC)
Calculation Steps:
- Calculate Volume: V = Length × Width × Thickness V = 20 cm × 15 cm × 0.3 cm = 90 cm³
- Find Density: The density of Polycarbonate (PC) is approximately 1.20 g/cm³.
- Calculate Weight: W = Volume × Density W = 90 cm³ × 1.20 g/cm³ = 108 grams
- Convert to Kilograms: W = 108 g / 1000 = 0.108 kg
Results:
- Volume: 90 cm³
- Density: 1.20 g/cm³
- Weight: 0.108 kg
Financial Interpretation: Knowing this weight is crucial for estimating raw material costs per unit, determining packaging requirements, and calculating shipping costs. If the production run is 10,000 units, the total raw plastic needed would be 1080 kg, influencing bulk purchasing decisions.
Example 2: Calculating the Weight of a Cylindrical Container Lid
Scenario: A manufacturer is producing lids for cylindrical containers. The lid is essentially a short cylinder.
Inputs:
- Shape: Cylinder
- Diameter: 10 cm (Radius = 5 cm)
- Height (Thickness of lid): 1.5 cm
- Plastic Type: Polypropylene (PP)
Calculation Steps:
- Calculate Volume: V = π × radius² × height V = π × (5 cm)² × 1.5 cm ≈ 3.14159 × 25 cm² × 1.5 cm ≈ 117.81 cm³
- Find Density: The density of Polypropylene (PP) is approximately 0.91 g/cm³.
- Calculate Weight: W = Volume × Density W = 117.81 cm³ × 0.91 g/cm³ ≈ 107.21 grams
- Convert to Kilograms: W = 107.21 g / 1000 ≈ 0.107 kg
Results:
- Volume: 117.81 cm³
- Density: 0.91 g/cm³
- Weight: 0.107 kg
Financial Interpretation: This weight information helps in accurately quoting prices to clients. If the selling price of the plastic material is $2 per kilogram, the raw material cost for each lid is approximately $0.214. This factor is critical for profitability analysis, especially for high-volume production.
How to Use This Plastic Weight Calculator
Our online calculator simplifies the process of determining the weight of plastic components. Follow these steps for accurate results:
Step-by-Step Instructions:
- Select Component Shape: Choose the basic geometric shape that best represents your plastic part from the 'Component Shape' dropdown menu (Cuboid, Cylinder, Sphere, Rectangular Prism).
- Enter Dimensions: Based on your selected shape, the calculator will prompt you to enter relevant dimensions (e.g., length, width, height, radius, diameter). Ensure you use consistent units, preferably centimeters (cm) for dimensions, as the calculator defaults to calculating volume in cubic centimeters (cm³).
- Choose Plastic Type: Select the type of plastic you are using from the 'Plastic Type' dropdown. The calculator will automatically populate the approximate density for common plastics like ABS, PC, HDPE, PP, PVC, PS, and PET.
- Enter Custom Density (If Needed): If you are using a plastic not listed or require a highly precise calculation, select 'Custom Density' from the dropdown. Then, enter the specific density value in g/cm³ into the 'Custom Density Value' field that appears.
- Calculate Weight: Click the "Calculate Weight" button.
How to Read Results:
The calculator will display:
- Primary Result (Large Font): The calculated weight of your plastic component in kilograms (kg).
- Intermediate Values:
- Volume: The calculated volume of the component in cubic centimeters (cm³).
- Density: The density of the selected plastic (or your custom input) in grams per cubic centimeter (g/cm³).
- Material: The name of the plastic used.
- Formula Used: A reminder of the basic formula: Weight = Volume × Density.
Decision-Making Guidance:
Use these results to:
- Cost Estimation: Multiply the calculated weight (in kg) by the cost per kilogram of your specific plastic resin to determine raw material costs.
- Shipping & Logistics: Input the weight into shipping calculators or compare it against weight limits for transportation.
- Design Optimization: If the weight is too high, explore ways to reduce the volume (e.g., thinner walls, different shape) while maintaining structural integrity.
- Material Sourcing: Ensure the density value used matches your actual sourced material for accuracy.
Key Factors That Affect Plastic Weight Results
While the basic formula (Weight = Volume × Density) is simple, several factors can influence the accuracy and practical application of plastic weight calculations:
- Volume Accuracy: The precision of your dimensional measurements directly impacts the calculated volume. Small errors in length, width, or height can lead to significant weight discrepancies, especially for large components. Using precise measurement tools and accounting for tolerances is vital.
- Material Density Variations: Standard density values are averages. Actual density can fluctuate due to:
- Additives & Fillers: Incorporating fillers (like glass fibers, talc, or minerals) to enhance properties significantly increases density. Colorants and other additives can also cause minor changes.
- Manufacturing Process: Injection molding, extrusion, and other processes can introduce variations in density, especially related to cooling rates and internal stresses.
- Specific Grade: Even within a single plastic type (e.g., HDPE), different grades can have slightly different density ranges.
- Temperature Effects: Plastic density changes with temperature. While this effect is usually minor at typical ambient conditions, it can become relevant for components operating in extreme heat or cold. The provided densities are typically at room temperature.
- Part Complexity & Design Features: Internal cavities, undercuts, or complex geometries can make volume calculation difficult. If a part is hollow or has complex internal structures, the simple geometric formulas may not suffice, leading to inaccurate volume and, consequently, weight estimates.
- Wall Thickness Variations: In injection molding, wall thickness can vary across a single part due to flow dynamics and cooling. Uniform wall thickness is an assumption in basic calculations; thicker sections will weigh more.
- Moisture Absorption: Some plastics are hygroscopic, meaning they absorb moisture from the air. This absorbed moisture adds a small amount of weight. While often negligible for short-term calculations, it can be a factor for components used in high-humidity environments over long periods.
- Tooling and Manufacturing Tolerances: The actual manufactured part may deviate slightly from the design dimensions due to molding tolerances. These deviations affect the final volume and weight.
Frequently Asked Questions (FAQ)
Q1: What is the density of common plastics?
A1: Densities vary. For example, Polyethylene (PE) is around 0.91-0.96 g/cm³, Polypropylene (PP) is around 0.90-0.91 g/cm³, Polystyrene (PS) is around 1.04-1.06 g/cm³, PVC is around 1.30-1.45 g/cm³, ABS is around 1.04-1.07 g/cm³, and Polycarbonate (PC) is around 1.19-1.22 g/cm³. These are approximate values.
Q2: How do I measure the dimensions for the calculator?
A2: Use a measuring tape, ruler, or calipers to measure the length, width, height, diameter, or radius as applicable to the shape. Ensure you measure the outermost dimensions for solid shapes. For complex parts, consider breaking them down into simpler geometric components or using CAD software for volume extraction.
Q3: Does the calculator account for hollow parts?
A3: The basic calculator assumes solid parts based on standard geometric formulas. For hollow parts (like pipes or containers with specific wall thicknesses), you would need to calculate the volume of the material used by subtracting the internal volume from the external volume, or by using the wall thickness directly if applicable (e.g., for sheets/plates).
Q4: Why is my calculated weight different from the actual part weight?
A4: Differences can arise from variations in material density (due to additives, fillers, or manufacturing processes), inaccuracies in dimensional measurements, the assumption of a solid part, or environmental factors like temperature and moisture. For critical applications, weigh a physical sample using a precision scale.
Q5: Can I use this calculator for recycled plastics?
A5: Yes, but you'll likely need to use the 'Custom Density' option. Recycled plastics can have varying densities depending on the source material and processing. Obtain the specific density data for the recycled plastic blend you are using for the most accurate results.
Q6: What is the difference between weight and mass?
A6: In everyday and most engineering contexts, 'weight' is used colloquially to mean 'mass'. Scientifically, mass is the amount of matter in an object (measured in kg or g), while weight is the force of gravity acting on that mass (measured in Newtons). This calculator determines mass, which is commonly referred to as weight in industry.
Q7: How does plastic weight impact shipping costs?
A7: Shipping costs are often based on either the volumetric weight (dimensional weight) or the actual weight of the package, whichever is greater. Heavier plastic components directly increase the actual weight, potentially leading to higher shipping fees, especially for bulk shipments. Efficient plastic weight calculation helps in accurate freight quoting.
Q8: Can I calculate the weight of plastic parts with metal inserts?
A8: This calculator is designed for pure plastic components. To calculate the weight of a part with metal inserts, you would calculate the plastic weight separately using this tool and then add the known weight of the metal inserts. Alternatively, you could calculate the total volume and use an average density weighted by the volume proportion of plastic and metal, but this is less precise.
Enter the length of the cuboid.
Enter the width of the cuboid.
Enter the height of the cuboid.
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break;
case 'cylinder':
html += `
Enter the diameter of the cylinder base.
Enter the height of the cylinder.
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break;
case 'sphere':
html += `
Enter the radius of the sphere.
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break;
case 'rectangular_prism': // Represents a sheet or plate
html += `
Enter the length of the sheet.
Enter the width of the sheet.
Enter the thickness of the sheet.
`;
break;
}
dimensionsInputDiv.innerHTML = html;
}
function updateDensity() {
var selectedPlastic = plasticTypeSelect.value;
var density = 0;
var materialName = "N/A";
if (selectedPlastic === "custom") {
customDensityInputDiv.style.display = 'block';
var customValue = parseFloat(customDensityValueInput.value);
if (!isNaN(customValue) && customValue > 0) {
density = customValue;
materialName = "Custom";
} else {
density = NaN; // Indicate invalid custom density
}
} else {
customDensityInputDiv.style.display = 'none';
if (plasticDensities.hasOwnProperty(selectedPlastic)) {
density = plasticDensities[selectedPlastic];
materialName = plasticTypeSelect.options[plasticTypeSelect.selectedIndex].text;
}
}
densityResultDiv.innerHTML = "Density: " + (isNaN(density) ? "–.–" : density.toFixed(2)) + " g/cm³";
materialResultDiv.innerHTML = "Material: " + materialName + "";
return density;
}
function validateInput(id, errorId, minValue = null, maxValue = null) {
var input = document.getElementById(id);
var errorDiv = document.getElementById(errorId);
var value = parseFloat(input.value);
var isValid = true;
errorDiv.style.display = 'none'; // Hide error initially
input.style.borderColor = 'var(–border-color)'; // Reset border
if (input.value.trim() === "") {
errorDiv.textContent = "This field cannot be empty.";
errorDiv.style.display = 'block';
input.style.borderColor = 'var(–error-color)';
isValid = false;
} else if (isNaN(value)) {
errorDiv.textContent = "Please enter a valid number.";
errorDiv.style.display = 'block';
input.style.borderColor = 'var(–error-color)';
isValid = false;
} else {
if (minValue !== null && value maxValue) {
errorDiv.textContent = "Value exceeds maximum limit.";
errorDiv.style.display = 'block';
input.style.borderColor = 'var(–error-color)';
isValid = false;
}
}
// Specific check for thickness being too small for meaningful calculation
if (id === "thicknessSheet" && value > 0 && value < 0.01) {
errorDiv.textContent = "Thickness is too small for practical calculation.";
errorDiv.style.display = 'block';
input.style.borderColor = 'var(–error-color)';
isValid = false;
}
return isValid ? value : NaN;
}
function calculateWeight() {
var volume = 0;
var selectedShape = shapeSelect.value;
// Volume Calculation
var dimsValid = true;
switch (selectedShape) {
case 'cuboid':
var length = validateInput('length', 'lengthError', 0);
var width = validateInput('width', 'widthError', 0);
var height = validateInput('height', 'heightError', 0);
if (!isNaN(length) && !isNaN(width) && !isNaN(height)) {
volume = length * width * height;
} else { dimsValid = false; }
break;
case 'cylinder':
var diameter = validateInput('diameterCyl', 'diameterCylError', 0);
var height = validateInput('heightCyl', 'heightCylError', 0);
if (!isNaN(diameter) && !isNaN(height)) {
var radius = diameter / 2;
volume = Math.PI * Math.pow(radius, 2) * height;
} else { dimsValid = false; }
break;
case 'sphere':
var radius = validateInput('radiusSphere', 'radiusSphereError', 0);
if (!isNaN(radius)) {
volume = (4 / 3) * Math.PI * Math.pow(radius, 3);
} else { dimsValid = false; }
break;
case 'rectangular_prism':
var lengthSheet = validateInput('lengthSheet', 'lengthSheetError', 0);
var widthSheet = validateInput('widthSheet', 'widthSheetError', 0);
var thicknessSheet = validateInput('thicknessSheet', 'thicknessSheetError', 0);
if (!isNaN(lengthSheet) && !isNaN(widthSheet) && !isNaN(thicknessSheet)) {
volume = lengthSheet * widthSheet * thicknessSheet;
} else { dimsValid = false; }
break;
}
var density = updateDensity(); // Updates density display and returns value
if (!dimsValid || isNaN(density) || volume === 0) {
resultDiv.textContent = "–.– kg";
volumeResultDiv.innerHTML = "Volume: –.– cm³";
if(dimsValid && !isNaN(density)) { // Only show volume if dims were valid
volumeResultDiv.innerHTML = "Volume: –.– cm³";
}
updateChart([]); // Clear chart if calculation fails
return;
}
// Calculate weight in grams first
var weightGrams = volume * density;
// Convert to kilograms
var weightKg = weightGrams / 1000;
// Display results
volumeResultDiv.innerHTML = "Volume: " + volume.toFixed(2) + " cm³";
resultDiv.textContent = weightKg.toFixed(3) + " kg"; // Display with 3 decimal places for precision
updateChart(volume, weightKg, density); // Update chart
}
function resetCalculator() {
shapeSelect.value = "cuboid";
document.getElementById("length").value = "10";
document.getElementById("width").value = "5";
document.getElementById("height").value = "2";
plasticTypeSelect.value = "abs";
customDensityValueInput.value = "";
document.getElementById("customDensityInput").style.display = 'none';
// Clear all error messages
var errorMessages = document.querySelectorAll('.error-message');
for (var i = 0; i < errorMessages.length; i++) {
errorMessages[i].style.display = 'none';
}
// Reset borders
var inputs = document.querySelectorAll('.input-group input, .input-group select');
for (var i = 0; i < inputs.length; i++) {
inputs[i].style.borderColor = 'var(–border-color)';
}
updateFormulaDisplay(); // Re-render dimensions form and formula text
calculateWeight(); // Recalculate with defaults
}
function copyResults() {
var mainResult = resultDiv.textContent;
var volumeText = volumeResultDiv.textContent;
var densityText = densityResultDiv.textContent;
var materialText = materialResultDiv.textContent;
var formulaText = formulaUsedDiv.textContent;
var copyString = "Plastic Weight Calculation Results:\n\n";
copyString += mainResult + "\n";
copyString += volumeText + "\n";
copyString += densityText + "\n";
copyString += materialText + "\n";
copyString += formulaText + "\n\n";
copyString += "Assumptions:\n";
copyString += "- Shape: " + shapeSelect.value + "\n";
copyString += "- Plastic Type: " + plasticTypeSelect.options[plasticTypeSelect.selectedIndex].text + "\n";
// Append dimensions to copy string dynamically
var currentShape = shapeSelect.value;
switch(currentShape) {
case 'cuboid':
copyString += "- Length: " + document.getElementById('length').value + " cm\n";
copyString += "- Width: " + document.getElementById('width').value + " cm\n";
copyString += "- Height: " + document.getElementById('height').value + " cm\n";
break;
case 'cylinder':
copyString += "- Diameter: " + document.getElementById('diameterCyl').value + " cm\n";
copyString += "- Height: " + document.getElementById('heightCyl').value + " cm\n";
break;
case 'sphere':
copyString += "- Radius: " + document.getElementById('radiusSphere').value + " cm\n";
break;
case 'rectangular_prism':
copyString += "- Length: " + document.getElementById('lengthSheet').value + " cm\n";
copyString += "- Width: " + document.getElementById('widthSheet').value + " cm\n";
copyString += "- Thickness: " + document.getElementById('thicknessSheet').value + " cm\n";
break;
}
if (plasticTypeSelect.value === 'custom') {
copyString += "- Custom Density Value Entered: " + customDensityValueInput.value + " g/cm³\n";
}
var textArea = document.createElement("textarea");
textArea.value = copyString;
textArea.style.position = "fixed";
textArea.style.left = "-9999px";
document.body.appendChild(textArea);
textArea.focus();
textArea.select();
try {
var successful = document.execCommand('copy');
var msg = successful ? 'successful' : 'unsuccessful';
console.log('Copying text command was ' + msg);
var copySuccess = document.getElementById('copySuccess');
copySuccess.style.display = 'block';
setTimeout(function() { copySuccess.style.display = 'none'; }, 3000);
} catch (err) {
console.log('Oops, unable to copy');
}
document.body.removeChild(textArea);
}
function initChart() {
var ctx = document.getElementById('weightVolumeChart').getContext('2d');
weightVolumeChart = new Chart(ctx, {
type: 'line',
data: {
labels: [], // Will be populated by updateChart
datasets: [{
label: 'Calculated Weight (kg)',
data: [], // Will be populated by updateChart
borderColor: 'var(–primary-color)',
backgroundColor: 'rgba(0, 74, 153, 0.1)',
fill: true,
tension: 0.1
}, {
label: 'Plastic Density (g/cm³)',
data: [], // Will be populated by updateChart
borderColor: 'var(–success-color)',
backgroundColor: 'rgba(40, 167, 69, 0.1)',
fill: false,
tension: 0.1
}]
},
options: {
responsive: true,
maintainAspectRatio: false,
scales: {
y: {
beginAtZero: true,
title: {
display: true,
text: 'Value'
}
},
x: {
title: {
display: true,
text: 'Component Volume (cm³)'
}
}
},
plugins: {
tooltip: {
callbacks: {
label: function(context) {
var label = context.dataset.label || '';
if (label) {
label += ': ';
}
if (context.parsed.y !== null) {
label += context.parsed.y.toFixed(3);
}
if (context.dataset.label === 'Plastic Density (g/cm³)') {
label = context.dataset.label + ': ' + context.dataset.data[context.dataIndex].toFixed(2) + ' g/cm³';
} else if (context.dataset.label === 'Calculated Weight (kg)') {
label = context.dataset.label + ': ' + context.dataset.data[context.dataIndex].toFixed(3) + ' kg';
}
return label;
}
}
}
}
}
});
}
function updateChart(currentVolume, currentWeight, currentDensity) {
var ctx = document.getElementById('weightVolumeChart').getContext('2d');
var chartData = weightVolumeChart.data;
// Generate data points for chart visualization
var volumes = [];
var weights = [];
var densities = []; // Display density as a constant line or step function
// Use current density for the chart
var fixedDensity = currentDensity;
var fixedMaterial = materialResultDiv.querySelector('span').textContent;
var fixedPlasticType = plasticTypeSelect.value;
// Determine a reasonable range for volume simulation
var maxSimulatedVolume = currentVolume * 3; // Simulate up to 3x the current volume
if (maxSimulatedVolume < 100) maxSimulatedVolume = 100; // Ensure a minimum range
if (isNaN(maxSimulatedVolume) || maxSimulatedVolume <= 0) maxSimulatedVolume = 1000;
var step = maxSimulatedVolume / 20; // Generate 20 points for the line
for (var v = 0; v <= maxSimulatedVolume; v += step) {
volumes.push(v);
// Calculate corresponding weight if density were constant
var simulatedWeight = (v * fixedDensity) / 1000; // Convert g to kg
weights.push(simulatedWeight);
densities.push(fixedDensity); // Keep density constant for the selected material
}
// Ensure the current calculation point is included if not already
if (currentVolume && !volumes.includes(currentVolume)) {
volumes.push(currentVolume);
weights.push(currentWeight);
densities.push(fixedDensity);
}
chartData.labels = volumes.map(function(v){ return v.toFixed(0); }); // Format volume labels
chartData.datasets[0].data = weights;
chartData.datasets[1].data = densities;
// Update dataset labels based on selected plastic
var selectedPlasticName = plasticTypeSelect.options[plasticTypeSelect.selectedIndex].text;
chartData.datasets[0].label = 'Weight (' + fixedMaterial + ')';
chartData.datasets[1].label = 'Density (' + fixedMaterial + ')';
// Adjust x-axis label based on shape if useful
var xAxisLabel = 'Component Volume (cm³)';
if (selectedShape === 'rectangular_prism') {
xAxisLabel = 'Sheet Volume (cm³)';
} else if (selectedShape === 'cylinder') {
xAxisLabel = 'Cylinder Volume (cm³)';
}
weightVolumeChart.options.scales.x.title.text = xAxisLabel;
weightVolumeChart.update();
}
// Initial setup
window.onload = function() {
updateDimensionsForm(shapeSelect.value);
updateDensity();
calculateWeight(); // Calculate with default values on load
initChart(); // Initialize the chart
};