Estimate your potential weight loss based on your daily calorie deficit. Enter your details below to see projected results.
The number of calories you consume less than you burn per day. A common deficit for ~1 lb/week loss is 500 kcal.
The total amount of weight you aim to lose.
Your current body fat percentage. This helps refine the calculation of lean body mass vs. fat mass to be lost. (Optional, can be estimated)
Your Projected Weight Loss
—
Estimated Time to Reach Goal
Estimated Fat Loss (lbs): —
Estimated Lean Mass Preserved (lbs): —
Total Calories Burned (kcal): —
Results copied to clipboard!
Formula Used
The calculation is based on the principle that approximately 3,500 calories equal one pound of body fat. We calculate the total calorie deficit needed to achieve your target weight loss and then divide that by your daily calorie deficit to estimate the time required. We also differentiate between fat loss and lean mass preservation.
Weight Loss Projection Over Time
Visualizing your estimated weight loss journey.
Weight Loss Variables Table
Variable
Meaning
Unit
Typical Range
Daily Calorie Deficit
Net difference between calories burned and calories consumed daily.
kcal/day
100 – 1000+
Target Weight Loss
Total desired reduction in body weight.
lbs
1 – 100+
Total Calories Burned
Total caloric deficit accumulated over the projection period.
kcal
Calculated
Estimated Fat Loss
Portion of weight loss attributed to fat reduction.
lbs
Calculated
Estimated Lean Mass Preserved
Portion of weight loss attributed to maintaining muscle mass (influenced by deficit size and body composition).
lbs
Calculated
Projected Time to Goal
Estimated duration to reach the target weight loss.
Days/Weeks/Months
Calculated
What is Expected Weight Loss Calculation?
{primary_keyword} is a crucial concept for anyone embarking on a weight loss journey. It's the process of estimating how much weight you can realistically lose over a specific period, based on your dietary habits and physical activity levels. Understanding how to calculate expected weight loss empowers you to set achievable goals and stay motivated.
This calculation is primarily used by individuals seeking to reduce their body weight for health, aesthetic, or performance reasons. It's a fundamental tool in personal fitness and nutrition planning. Common misconceptions include believing that drastic, rapid weight loss is sustainable or healthy, or that all weight lost is purely fat.
For instance, a person aiming to lose weight uses this calculation to understand the timeline of their goal, which is key for long-term adherence. Athletes might use it to hit specific weight classes for competitions. It's also a valuable tool for healthcare professionals guiding patients through weight management programs. We use the fundamental principle that a calorie deficit drives weight loss. For a detailed understanding, exploring resources on calorie deficit vs. calorie surplus can be very insightful.
{primary_keyword} Formula and Mathematical Explanation
The core of how to calculate expected weight loss relies on the well-established fact that one pound of body fat is equivalent to approximately 3,500 calories. Therefore, to lose one pound of fat, you need to create a deficit of 3,500 calories.
The primary formula is: Time to Lose Weight (in days) = (Target Weight Loss in lbs * 3500) / Daily Calorie Deficit
Let's break down the variables and additional calculations:
Daily Calorie Deficit (DCD): This is the difference between your Total Daily Energy Expenditure (TDEE) and your daily calorie intake. For example, if your TDEE is 2500 kcal and you consume 2000 kcal, your DCD is 500 kcal.
Target Weight Loss (TWL): The total number of pounds you wish to lose.
Total Calorie Deficit Needed (TCDN): This is calculated as TWL * 3500 kcal/lb.
Estimated Time to Reach Goal (Days): Calculated as TCDN / DCD. This can then be converted into weeks or months.
Estimated Fat Loss (lbs): In a moderate deficit, most weight loss is fat. This is approximated as TWL, assuming the deficit is primarily targeting fat.
Estimated Lean Mass Preserved (lbs): This accounts for the non-fat components of body weight (muscle, water, etc.). A very large deficit can lead to significant lean mass loss. A moderate deficit (like 500-750 kcal) tends to preserve lean mass better. For simplicity in this calculator, we assume a portion of the loss might be lean mass, especially if the deficit is very large or the individual is already lean. A common assumption is that ~75-80% of weight lost in a moderate deficit is fat, while ~20-25% could be lean mass or water. However, for simplicity and to provide a clear projection based on the deficit alone, we present it as a residual from the total target. A more sophisticated model would incorporate activity levels and protein intake.
Weight Loss Variables Details
Variable
Meaning
Unit
Typical Range/Notes
Daily Calorie Deficit
The net difference between calories burned and calories consumed per day.
kcal/day
100 – 1000+ (Higher deficit can lead to faster loss but may risk muscle loss and adherence issues.)
Target Weight Loss
The total amount of weight an individual aims to lose.
lbs
1 – 100+ (Depends on individual goals and starting point.)
3500 kcal/lb
The approximate caloric energy stored in one pound of body fat.
kcal/lb
Constant scientific value.
Total Calorie Deficit Needed
The cumulative calorie deficit required to lose the target weight.
kcal
Calculated (TWL * 3500)
Estimated Time to Reach Goal
The projected duration in days to achieve the target weight loss.
Days
Calculated (TCDN / DCD)
Estimated Fat Loss
The portion of the target weight loss expected to be fat mass.
lbs
Often assumed to be close to TWL in moderate deficits.
Estimated Lean Mass Preserved
The portion of weight loss that is NOT fat, ideally preserved muscle mass.
lbs
Calculated as TWL – Estimated Fat Loss, influenced by deficit size and diet.
Current Body Fat Percentage
The percentage of an individual's total body weight that is fat mass.
%
10% – 60%+ (Used for more advanced estimations of body composition.)
Practical Examples (Real-World Use Cases)
Let's explore some scenarios for how to calculate expected weight loss:
Example 1: Moderate Weight Loss Goal
Scenario: Sarah wants to lose 15 lbs. She has calculated her TDEE to be 2200 kcal and aims to consume 1700 kcal per day. This gives her a daily calorie deficit of 500 kcal.
Estimated Time to Reach Goal = 52,500 kcal / 500 kcal/day = 105 days
Estimated Fat Loss = 15 lbs (assuming most is fat in moderate deficit)
Estimated Lean Mass Preserved = 0 lbs (for simplicity in this example, meaning all target loss is fat)
Interpretation: Sarah can expect to lose 15 lbs in approximately 105 days (about 3.5 months) if she consistently maintains a 500 kcal daily deficit. This is a sustainable rate of weight loss (around 1-1.5 lbs per week).
Example 2: Faster Weight Loss Goal with Higher Deficit
Scenario: Mark needs to lose 20 lbs relatively quickly for a specific event. His TDEE is 2800 kcal, and he plans to consume 1800 kcal, creating a 1000 kcal daily deficit. He is concerned about muscle loss.
Estimated Time to Reach Goal = 70,000 kcal / 1000 kcal/day = 70 days
Estimated Fat Loss = 17 lbs (assuming ~85% of loss is fat with higher deficit and good protein intake)
Estimated Lean Mass Preserved = 3 lbs (assuming ~15% of loss is non-fat mass)
Interpretation: Mark could potentially lose 20 lbs in about 70 days (10 weeks) with a 1000 kcal deficit. However, the calculator highlights that a portion of this loss might be lean mass. To mitigate this, Mark should ensure adequate protein intake and incorporate strength training, which are crucial factors in preserving muscle mass during dieting. You can learn more about optimizing your diet by reading our guide on macronutrient ratios for weight loss.
How to Use This {primary_keyword} Calculator
Our calculator is designed for ease of use, providing quick estimates for your weight loss journey. Follow these steps:
Enter Daily Calorie Deficit: Input the number of calories you plan to be in deficit each day. A common starting point is 500 kcal, which aims for approximately 1 lb of fat loss per week.
Enter Target Weight Loss: Specify the total number of pounds you aim to lose.
Enter Current Body Fat Percentage (Optional): While not strictly required for the basic calculation, providing this can help refine the understanding of fat loss versus lean mass preservation in more advanced models. For this calculator, it primarily serves as a data point for context.
Click 'Calculate': The calculator will instantly display your primary result: the estimated time to reach your goal.
Review Intermediate Values: Check the estimated fat loss and lean mass preserved figures for a more nuanced view of your potential body composition changes.
Understand the Explanation: Read the brief formula explanation below the calculator to grasp the underlying principles.
Visualize with the Chart: The dynamic chart shows your projected weight loss progress over the estimated timeframe.
Use the 'Copy Results' Button: Save your projected outcomes and key assumptions for your records or to share with a trainer or nutritionist.
Utilize the 'Reset' Button: If you want to start over or try different scenarios, the reset button restores default values.
Decision-Making Guidance: Use the results to set realistic expectations. If the projected time is too long, consider if a slightly larger, sustainable deficit is appropriate for you, or if focusing on increasing activity to burn more calories is a better approach. Conversely, if the projected time is very short, be mindful of the potential for muscle loss and ensure you are supporting your body adequately.
Key Factors That Affect {primary_keyword} Results
While the calorie deficit is the cornerstone of weight loss, several other factors significantly influence the actual outcomes:
Metabolic Adaptation: As you lose weight, your metabolism can slow down (adaptive thermogenesis), meaning your TDEE decreases. This can make continued weight loss harder and might require further adjustments to your diet or activity. This is a key reason why results can slow over time compared to initial projections.
Muscle Mass Preservation: If your calorie deficit is too aggressive, or if you don't consume enough protein and engage in resistance training, you risk losing muscle mass along with fat. Muscle is metabolically active and important for overall health and body composition. Our calculator estimates lean mass preservation, but this is heavily influenced by lifestyle choices.
Dietary Adherence: Consistently sticking to your calorie deficit is paramount. Fluctuations, weekend binges, or inaccurate tracking can derail progress, making the calculated timeline less reliable. The psychological aspect of sustainable dieting strategies is often more important than the precise number.
Hormonal Factors: Hormones like cortisol, thyroid hormones, and sex hormones can influence appetite, fat storage, and metabolism, thereby affecting weight loss rates. Conditions like PCOS or thyroid dysfunction can complicate weight loss efforts.
Sleep Quality and Stress Levels: Poor sleep and high stress can increase cortisol levels, which can promote fat storage (especially around the abdomen) and increase appetite for calorie-dense foods, hindering weight loss.
Hydration: Adequate water intake is essential for metabolism and can help manage hunger. Dehydration can sometimes be mistaken for hunger.
Exercise Type and Intensity: While the calculator focuses on calorie deficit, the *type* of calories burned matters. Cardiovascular exercise burns calories directly, while strength training builds muscle, boosting resting metabolism and improving body composition. Both are vital for effective and healthy weight loss. Understanding the role of cardio vs. strength training is beneficial.
Individual Biological Responses: Genetics, age, sex, and baseline health can all influence how individuals respond to a calorie deficit. Some people naturally lose weight faster or slower than others, even with similar deficits.
A safe and sustainable rate of weight loss is generally considered to be 1-2 pounds per week. This typically requires a daily calorie deficit of 500-1000 calories.
Can I lose weight faster than the calculator suggests?
You can achieve faster weight loss with a larger calorie deficit, but this often comes at the cost of increased muscle loss, fatigue, nutrient deficiencies, and potential long-term metabolic issues. It is generally not recommended for sustainability.
Does the calculator account for water weight?
The primary calculation focuses on fat loss (3500 kcal/lb). Initial weight loss often includes a significant amount of water weight, especially when reducing carbohydrate intake. This calculator provides a projection based on fat loss, and actual scale changes may fluctuate more rapidly initially due to water.
What if my daily calorie deficit is not consistent?
Consistency is key. If your deficit varies significantly day-to-day, the average deficit over time is what matters. However, large fluctuations can make the projected timeline less accurate. Aim for consistency as much as possible.
How does body fat percentage affect weight loss calculations?
While this calculator uses it for context, for more advanced calculations, a higher body fat percentage generally means a larger proportion of weight lost will be fat, and a greater capacity to preserve muscle with a deficit. Individuals with lower body fat need to be more cautious about muscle loss.
Is it possible to lose weight without a calorie deficit?
In very specific circumstances (e.g., extreme dehydration, loss of limb), yes. However, for typical body fat reduction, a calorie deficit is the fundamental requirement. Other factors influence *how* that deficit is achieved and what is lost (fat vs. muscle).
What should I do if my weight loss stalls?
Plateaus are common. They can occur due to metabolic adaptation, inaccurate calorie tracking, or changes in fluid retention. Strategies include re-evaluating calorie intake, increasing physical activity, ensuring adequate sleep and stress management, and potentially taking a diet break.
How does the 3500 kcal/lb rule hold up?
The 3500 kcal/lb rule is a widely cited estimate and a useful rule of thumb. While individual metabolic responses can vary, and the exact composition of weight lost (fat vs. lean mass vs. water) can differ, it remains a practical basis for planning and understanding weight loss timelines.
Tips and strategies for building a sustainable healthy diet for long-term results.
var chartInstance = null;
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var errorElement = document.getElementById(id + "Error");
var value = parseFloat(element.value);
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return true;
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function calculateWeightLoss() {
var valid = true;
valid = validateInput("dailyCalorieDeficit", 1) && valid;
valid = validateInput("targetWeightLoss", 1) && valid;
valid = validateInput("bodyFatPercentage", 0, 100) && valid;
if (!valid) {
return;
}
var dailyCalorieDeficit = parseFloat(document.getElementById("dailyCalorieDeficit").value);
var targetWeightLoss = parseFloat(document.getElementById("targetWeightLoss").value);
var bodyFatPercentage = parseFloat(document.getElementById("bodyFatPercentage").value);
var kcalPerPoundFat = 3500;
var totalCalorieDeficitNeeded = targetWeightLoss * kcalPerPoundFat;
var estimatedTimeDays = totalCalorieDeficitNeeded / dailyCalorieDeficit;
// Distribute loss between fat and lean mass. A common, albeit simplified, approach:
// Assume a significant portion is fat, and the rest is lean mass if deficit is high.
// For this calculator, let's assume ~80% fat loss in moderate deficits, and maybe 70-75% in higher deficits,
// but for simplicity, we'll make it directly proportional to target loss with a modifier for very high deficits.
// A more robust model would factor in body fat %. For now, we use a simpler proportion.
var estimatedFatLoss;
var estimatedLeanMassPreserved;
if (dailyCalorieDeficit >= 1000) { // Higher deficit
estimatedFatLoss = targetWeightLoss * 0.75; // ~75% fat
estimatedLeanMassPreserved = targetWeightLoss * 0.25; // ~25% lean mass/water
} else if (dailyCalorieDeficit >= 500) { // Moderate deficit
estimatedFatLoss = targetWeightLoss * 0.85; // ~85% fat
estimatedLeanMassPreserved = targetWeightLoss * 0.15; // ~15% lean mass/water
} else { // Lower deficit
estimatedFatLoss = targetWeightLoss * 0.90; // ~90% fat
estimatedLeanMassPreserved = targetWeightLoss * 0.10; // ~10% lean mass/water
}
// Ensure values are not negative due to rounding or edge cases
estimatedFatLoss = Math.max(0, estimatedFatLoss);
estimatedLeanMassPreserved = Math.max(0, estimatedLeanMassPreserved);
var totalCaloriesBurned = totalCalorieDeficitNeeded;
// Display results
document.getElementById("primaryResult").textContent = formatDuration(estimatedTimeDays);
document.getElementById("estimatedFatLoss").textContent = estimatedFatLoss.toFixed(1) + " lbs";
document.getElementById("estimatedLeanMassPreserved").textContent = estimatedLeanMassPreserved.toFixed(1) + " lbs";
document.getElementById("totalCaloriesBurned").textContent = totalCaloriesBurned.toFixed(0) + " kcal";
updateChart(estimatedTimeDays, targetWeightLoss, estimatedFatLoss, estimatedLeanMassPreserved);
// Show the results section
document.getElementById("results").style.display = "block";
}
function formatDuration(days) {
if (days < 1) return "Less than a day";
if (days < 7) return Math.round(days) + " days";
var weeks = days / 7;
if (weeks < 4.3) return weeks.toFixed(1) + " weeks";
var months = days / 30.44; // Average days in a month
return months.toFixed(1) + " months";
}
function resetCalculator() {
document.getElementById("dailyCalorieDeficit").value = "500";
document.getElementById("targetWeightLoss").value = "10";
document.getElementById("bodyFatPercentage").value = "30";
document.getElementById("dailyCalorieDeficitError").textContent = "";
document.getElementById("dailyCalorieDeficitError").classList.remove("visible");
document.getElementById("targetWeightLossError").textContent = "";
document.getElementById("targetWeightLossError").classList.remove("visible");
document.getElementById("bodyFatPercentageError").textContent = "";
document.getElementById("bodyFatPercentageError").classList.remove("visible");
document.getElementById("primaryResult").textContent = "–";
document.getElementById("estimatedFatLoss").textContent = "–";
document.getElementById("estimatedLeanMassPreserved").textContent = "–";
document.getElementById("totalCaloriesBurned").textContent = "–";
if (chartInstance) {
chartInstance.destroy();
chartInstance = null;
}
// Clear canvas and hide results/chart if reset
var canvas = document.getElementById("weightLossChart");
var ctx = canvas.getContext("2d");
ctx.clearRect(0, 0, canvas.width, canvas.height);
document.getElementById("results").style.display = "none";
}
function copyResults() {
var primaryResult = document.getElementById("primaryResult").textContent;
var estimatedFatLoss = document.getElementById("estimatedFatLoss").textContent;
var estimatedLeanMassPreserved = document.getElementById("estimatedLeanMassPreserved").textContent;
var totalCaloriesBurned = document.getElementById("totalCaloriesBurned").textContent;
var dailyDeficit = document.getElementById("dailyCalorieDeficit").value;
var targetLoss = document.getElementById("targetWeightLoss").value;
var bodyFat = document.getElementById("bodyFatPercentage").value;
var textToCopy = "— Projected Weight Loss —\n";
textToCopy += "Estimated Time: " + primaryResult + "\n";
textToCopy += "Estimated Fat Loss: " + estimatedFatLoss + "\n";
textToCopy += "Estimated Lean Mass Preserved: " + estimatedLeanMassPreserved + "\n";
textToCopy += "Total Calories Burned: " + totalCaloriesBurned + "\n\n";
textToCopy += "— Key Assumptions —\n";
textToCopy += "Daily Calorie Deficit: " + dailyDeficit + " kcal\n";
textToCopy += "Target Weight Loss: " + targetLoss + " lbs\n";
textToCopy += "Body Fat Percentage: " + bodyFat + " %\n";
navigator.clipboard.writeText(textToCopy).then(function() {
var successMessage = document.getElementById("copySuccessMessage");
successMessage.style.display = "block";
setTimeout(function() {
successMessage.style.display = "none";
}, 3000);
}).catch(function(err) {
console.error("Could not copy text: ", err);
alert("Failed to copy results. Please copy manually.");
});
}
function updateChart(estimatedTimeDays, targetWeightLoss, estimatedFatLoss, estimatedLeanMassPreserved) {
var canvas = document.getElementById('weightLossChart');
var ctx = canvas.getContext('2d');
// Clear previous chart if it exists
if (chartInstance) {
chartInstance.destroy();
}
// Define chart dimensions dynamically based on canvas size
var chartWidth = canvas.parentElement.clientWidth;
var chartHeight = 300; // Fixed height or could be dynamic
canvas.width = chartWidth;
canvas.height = chartHeight;
// Data points for the chart
var dataPoints = [];
var steps = 50; // Number of points to plot
for (var i = 0; i 0) ? targetWeightLoss * progress : 0;
// Distribute the loss between fat and lean mass proportionally
var currentFatLoss = estimatedFatLoss * progress;
var currentLeanMassLost = estimatedLeanMassPreserved * progress;
// The 'weight lost' represented on the Y-axis could be total loss
// Or we could show fat vs lean mass as separate lines. Let's do total loss first, and fat loss.
// And show lean mass change as a secondary aspect.
dataPoints.push({
x: currentDays,
totalLoss: currentWeightLoss,
fatLoss: currentFatLoss,
leanMassLost: currentLeanMassLost
});
}
// Prepare labels and datasets for Chart.js (simulated)
var labels = dataPoints.map(function(dp) {
return formatDuration(dp.x);
});
var totalLossData = dataPoints.map(function(dp) {
return dp.totalLoss;
});
var fatLossData = dataPoints.map(function(dp) {
return dp.fatLoss;
});
var leanMassLostData = dataPoints.map(function(dp) {
// This represents the amount of lean mass lost, not preserved.
// For clarity on the chart, maybe better to show preserved mass relative to start.
// Or just focus on total loss and fat loss for simplicity.
return dp.leanMassLost;
});
// Simple line chart rendering using native canvas API
var chart = new Chart(ctx, {
type: 'line',
data: {
labels: labels,
datasets: [{
label: 'Total Weight Loss (lbs)',
data: totalLossData,
borderColor: 'rgba(0, 74, 153, 1)', // Primary color
backgroundColor: 'rgba(0, 74, 153, 0.1)',
fill: false,
tension: 0.1
}, {
label: 'Estimated Fat Loss (lbs)',
data: fatLossData,
borderColor: 'rgba(40, 167, 69, 1)', // Success color
backgroundColor: 'rgba(40, 167, 69, 0.1)',
fill: false,
tension: 0.1
}]
},
options: {
responsive: true,
maintainAspectRatio: false,
scales: {
x: {
title: {
display: true,
labelString: 'Time to Goal'
}
},
y: {
title: {
display: true,
labelString: 'Weight Loss (lbs)'
},
beginAtZero: true
}
},
plugins: {
tooltip: {
callbacks: {
footer: function(tooltipItems) {
var item = tooltipItems[0];
var dp = dataPoints[item.dataIndex];
return [
'Fat Loss: ' + dp.fatLoss.toFixed(1) + ' lbs',
'Lean Mass Lost: ' + dp.leanMassLost.toFixed(1) + ' lbs'
];
}
}
}
}
}
});
chartInstance = chart; // Store instance to destroy later
}
// Initial calculation on load
document.addEventListener("DOMContentLoaded", function() {
calculateWeightLoss();
// Hide results initially if they are not set
document.getElementById("results").style.display = "none";
});
// Chart.js integration (needs to be included via CDN or locally)
// For this example, we assume Chart.js is available.
// If running locally without Chart.js, this chart part will fail.
// A pure SVG or canvas implementation would be needed if Chart.js is not allowed.
// Re-implementing using pure canvas API below.
// **IMPORTANT**: This requires Chart.js library to be included in your HTML for the above to work.
// If you need a pure JS/Canvas/SVG chart, that would require significant additional code.
// Let's proceed with the Chart.js dependency assumption for now.
// **NOTE**: The provided code assumes Chart.js library is available.
// If Chart.js is NOT available, the 'updateChart' function would need to be
// completely rewritten using native Canvas API or SVG to draw the chart.
// For demonstration, we will provide a placeholder for Chart.js inclusion.
// In a real-world scenario, you'd add:
//
// before the closing or before the script tag above.
// **Self-Correction**: The prompt strictly says "NO external libraries".
// Therefore, the Chart.js dependency is invalid.
// I must re-implement `updateChart` using pure Canvas API.
// — REIMPLEMENTATION of updateChart using native Canvas API —
function updateChart(estimatedTimeDays, targetWeightLoss, estimatedFatLoss, estimatedLeanMassPreserved) {
var canvas = document.getElementById('weightLossChart');
var ctx = canvas.getContext('2d');
var chartWidth = canvas.parentElement.clientWidth;
var chartHeight = 300;
canvas.width = chartWidth;
canvas.height = chartHeight;
ctx.clearRect(0, 0, canvas.width, canvas.height); // Clear canvas
if (estimatedTimeDays <= 0 || targetWeightLoss <= 0) {
ctx.font = '16px Arial';
ctx.fillStyle = '#6c757d';
ctx.textAlign = 'center';
ctx.fillText('Enter valid inputs to see the chart.', canvas.width / 2, canvas.height / 2);
return;
}
var margin = { top: 20, right: 30, bottom: 50, left: 60 };
var plotWidth = chartWidth – margin.left – margin.right;
var plotHeight = chartHeight – margin.top – margin.bottom;
// Scale calculations
var xScale = plotWidth / estimatedTimeDays;
var yScale = plotHeight / targetWeightLoss;
// Draw Axes
ctx.strokeStyle = '#ccc';
ctx.lineWidth = 1;
// Y-axis
ctx.beginPath();
ctx.moveTo(margin.left, margin.top);
ctx.lineTo(margin.left, chartHeight – margin.bottom);
ctx.stroke();
// X-axis
ctx.beginPath();
ctx.moveTo(margin.left, chartHeight – margin.bottom);
ctx.lineTo(chartWidth – margin.right, chartHeight – margin.bottom);
ctx.stroke();
// Y-axis Labels and Ticks
ctx.fillStyle = '#333';
ctx.textAlign = 'right';
ctx.font = '12px Arial';
var yTickCount = 5;
for (var i = 0; i <= yTickCount; i++) {
var yValue = (targetWeightLoss / yTickCount) * i;
var yPos = chartHeight – margin.bottom – (yValue * yScale);
ctx.fillText(yValue.toFixed(0) + ' lbs', margin.left – 10, yPos + 5);
ctx.beginPath();
ctx.moveTo(margin.left – 5, yPos);
ctx.lineTo(margin.left, yPos);
ctx.stroke();
}
// X-axis Labels and Ticks
ctx.textAlign = 'center';
var xTickCount = Math.min(5, Math.ceil(estimatedTimeDays / 7)); // Aim for max 5 ticks, at least weekly
var tickIntervalDays = estimatedTimeDays / xTickCount;
for (var i = 0; i chartWidth – margin.right) xPos = chartWidth – margin.right; // Cap at right edge
var label = formatDuration(xValueDays);
ctx.fillText(label, xPos, chartHeight – margin.bottom + 20);
ctx.beginPath();
ctx.moveTo(xPos, chartHeight – margin.bottom);
ctx.lineTo(xPos, chartHeight – margin.bottom + 5);
ctx.stroke();
}
// Draw Labels
ctx.font = '16px Arial';
ctx.fillStyle = 'rgba(0, 74, 153, 1)';
ctx.textAlign = 'left';
ctx.fillText('Total Weight Loss', margin.left + 5, margin.top + 20);
ctx.fillStyle = 'rgba(40, 167, 69, 1)';
ctx.fillText('Fat Loss', margin.left + 5, margin.top + 40);
// Draw Lines
// Total Loss Line
ctx.beginPath();
ctx.strokeStyle = 'rgba(0, 74, 153, 1)';
ctx.lineWidth = 2;
ctx.moveTo(margin.left, chartHeight – margin.bottom); // Start at 0,0 point relative to plot area
ctx.lineTo(margin.left + (estimatedTimeDays * xScale), margin.top); // End at max time, max loss
ctx.stroke();
// Fat Loss Line
ctx.beginPath();
ctx.strokeStyle = 'rgba(40, 167, 69, 1)';
ctx.lineWidth = 2;
ctx.moveTo(margin.left, chartHeight – margin.bottom); // Start at 0,0 point
var fatLossEndPointY = chartHeight – margin.bottom – (estimatedFatLoss * yScale);
var fatLossEndPointX = margin.left + (estimatedTimeDays * xScale);
// Ensure fat loss line doesn't exceed total loss line (conceptually)
// And ensure it doesn't go below the plot area if calculation is weird.
if (fatLossEndPointY chartHeight – margin.bottom) fatLossEndPointY = chartHeight – margin.bottom;
ctx.lineTo(fatLossEndPointX, fatLossEndPointY);
ctx.stroke();
// Mark the final target point for total loss
ctx.fillStyle = 'rgba(0, 74, 153, 1)';
ctx.beginPath();
ctx.arc(margin.left + (estimatedTimeDays * xScale), margin.top, 5, 0, Math.PI * 2);
ctx.fill();
// Mark the final target point for fat loss
ctx.fillStyle = 'rgba(40, 167, 69, 1)';
ctx.beginPath();
ctx.arc(fatLossEndPointX, fatLossEndPointY, 5, 0, Math.PI * 2);
ctx.fill();
// Add a simple legend/tooltip simulation within the plot area or nearby
ctx.fillStyle = '#333′;
ctx.font = '11px Arial';
ctx.textAlign = 'left';
var legendX = margin.left + 5;
var legendY = margin.top + 60;
ctx.fillText('Data represents projected loss over time.', legendX, legendY);
}