Bmi Goal Weight Calculator

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BMI Goal Weight Calculator

Calculate Your Goal Weight

Your Target Weight
Current BMI
Desired BMI
Weight Difference
Formula: Goal Weight = Desired BMI × (Height in meters)² This calculator helps you find a healthy target weight by inputting your current height and a desired BMI value. It then calculates the weight associated with that BMI.
Enter your height in centimeters (cm).
Height cannot be empty or negative.
Enter your current weight in kilograms (kg).
Weight cannot be empty or negative.
Enter a target BMI (e.g., 18.5-24.9 for healthy range).
Desired BMI cannot be empty, negative, or zero.
BMI Ranges and Your Goal
BMI Category BMI Range Health Implications
Underweight Less than 18.5 May indicate malnutrition, osteoporosis, or other issues.
Healthy Weight 18.5 – 24.9 Associated with lower risk of chronic diseases.
Overweight 25 – 29.9 Increased risk of heart disease, diabetes, and other conditions.
Obesity (Class I) 30 – 34.9 Significantly increased risk of health problems.
Obesity (Class II) 35 – 39.9 High risk of severe health complications.
Obesity (Class III) 40 or greater Extreme risk of serious health problems.

What is a BMI Goal Weight?

A BMI goal weight calculator is a specialized tool designed to help individuals understand and set realistic weight targets based on their height and desired Body Mass Index (BMI). Instead of just calculating a current BMI, this calculator focuses on projecting a target weight that aligns with a specific BMI value, often within the 'healthy' range. It's a fundamental resource for anyone embarking on a weight management journey, whether aiming for weight loss or weight gain, to establish a scientifically-backed objective. Understanding your BMI goal weight provides a clear benchmark for progress and helps in setting achievable health milestones. It's a crucial step in a comprehensive health and fitness plan.

Who Should Use a BMI Goal Weight Calculator?

This calculator is beneficial for a wide range of individuals:

  • Those aiming for weight loss: By setting a target weight within the healthy BMI range, you can define how much weight you need to lose.
  • Individuals seeking to gain weight: For those who are underweight, the calculator can help determine a healthy target weight to reach.
  • Health-conscious individuals: Anyone looking to maintain a healthy weight and understand their ideal weight range for their height.
  • Fitness enthusiasts: Athletes and active individuals may use it to fine-tune their body composition for optimal performance.
  • People with specific health conditions: Under the guidance of a healthcare professional, it can aid in managing conditions affected by weight.

Common Misconceptions About BMI Goal Weight

Several myths surround BMI and goal weights. It's important to clarify these:

  • BMI is a perfect measure of health: BMI does not distinguish between muscle and fat. A very muscular person might have a high BMI but be very healthy. Similarly, a person with low muscle mass might have a 'healthy' BMI but be unhealthy.
  • There's only one 'ideal' weight: Healthy weight ranges are broad. A "healthy BMI" is a range, not a single number, and individual needs vary. Our BMI goal weight calculator shows a range.
  • Reaching a goal weight automatically means optimal health: While reaching a healthy weight is a significant step, overall health also depends on diet, exercise, sleep, stress management, and other lifestyle factors.
  • BMI applies universally: BMI calculations can be less accurate for certain populations, such as children, the elderly, pregnant women, and highly trained athletes.

BMI Goal Weight Formula and Mathematical Explanation

The Core Formula

The foundation of any BMI goal weight calculator lies in the fundamental BMI formula, rearranged to solve for weight:

BMI = Weight (kg) / (Height (m))²

To find the goal weight, we isolate 'Weight' and use a desired BMI value:

Goal Weight (kg) = Desired BMI × (Height (m))²

Step-by-Step Derivation

  1. Start with the BMI formula: BMI = Weight / Height²
  2. Convert height to meters: If height is given in centimeters (cm), divide by 100 to get meters (m). For example, 170 cm = 1.70 m.
  3. Square the height in meters: Calculate Height (m) × Height (m). For 1.70 m, this is 1.70 × 1.70 = 2.89 m².
  4. Multiply by the desired BMI: Take your target BMI value (e.g., 22) and multiply it by the squared height. For our example: 22 × 2.89 = 63.58 kg. This is your BMI goal weight.

Variable Explanations

Understanding the variables is key to using the BMI goal weight calculator accurately:

Variable Meaning Unit Typical Range
Height The vertical measurement from the sole of the foot to the top of the head. Must be consistent. Centimeters (cm) for input, converted to Meters (m) for calculation. 140 cm – 210 cm (approx.)
Current Weight The person's current mass. Kilograms (kg) 30 kg – 200 kg (approx.)
Desired BMI The target Body Mass Index value the user wishes to achieve. Typically chosen from the 'healthy' range. Unitless (kg/m²) 17.0 – 40.0 (covering underweight to severe obesity)
Current BMI The calculated BMI based on current height and weight. Unitless (kg/m²) Calculated dynamically.
Goal Weight The calculated weight corresponding to the Desired BMI and the user's height. Kilograms (kg) Calculated dynamically.
Weight Difference The difference between current weight and goal weight. Kilograms (kg) Calculated dynamically.

Practical Examples (Real-World Use Cases)

Example 1: Weight Loss Goal

Scenario: Sarah is 165 cm tall and weighs 75 kg. She wants to know what weight she should aim for to have a BMI of 22 (which falls within the healthy range).

  • Inputs: Height = 165 cm, Current Weight = 75 kg, Desired BMI = 22
  • Calculations:
    • Height in meters = 165 / 100 = 1.65 m
    • Squared height = 1.65 m * 1.65 m = 2.7225 m²
    • Current BMI = 75 kg / 2.7225 m² ≈ 27.5 (Overweight)
    • Goal Weight = 22 * 2.7225 m² ≈ 59.9 kg
    • Weight Difference = 75 kg – 59.9 kg ≈ 15.1 kg
  • Interpretation: To achieve a BMI of 22, Sarah needs to reach a goal weight of approximately 59.9 kg. This means she aims to lose about 15.1 kg. Her current BMI of 27.5 indicates she is in the overweight category. This BMI goal weight calculation provides a clear target.

Example 2: Weight Gain Goal

Scenario: Mark is 180 cm tall and weighs 65 kg. He wants to reach a healthier weight and aims for a BMI of 20.

  • Inputs: Height = 180 cm, Current Weight = 65 kg, Desired BMI = 20
  • Calculations:
    • Height in meters = 180 / 100 = 1.80 m
    • Squared height = 1.80 m * 1.80 m = 3.24 m²
    • Current BMI = 65 kg / 3.24 m² ≈ 20.06 (Healthy Weight)
    • Goal Weight = 20 * 3.24 m² = 64.8 kg
    • Weight Difference = 64.8 kg – 65 kg ≈ -0.2 kg
  • Interpretation: Mark's current weight is already very close to a healthy BMI of 20. His goal weight is approximately 64.8 kg. The calculator shows minimal difference needed. If his desired BMI was higher, e.g., 23, his goal weight would be 23 * 3.24 m² = 74.5 kg, indicating a need to gain weight. This demonstrates how the BMI goal weight tool adapts.

How to Use This BMI Goal Weight Calculator

Using our BMI goal weight calculator is straightforward. Follow these steps to understand your target weight and health metrics:

  1. Enter Your Height: Input your height accurately in centimeters (cm) into the "Your Height" field. Ensure you are standing straight for an accurate measurement.
  2. Enter Your Current Weight: Provide your current weight in kilograms (kg) in the "Your Current Weight" field.
  3. Set Your Desired BMI: In the "Desired BMI" field, enter the target BMI value you wish to achieve. A common healthy range is between 18.5 and 24.9. You can choose a specific number within this range or slightly outside it based on your health goals or recommendations from a healthcare provider.
  4. Click "Calculate Goal Weight": Once all fields are filled, click the button. The calculator will instantly display:
    • Your Target Weight (the main result).
    • Your Current BMI.
    • Your Desired BMI.
    • The Weight Difference (how much weight you need to gain or lose).

Reading Your Results

The primary result highlights your BMI goal weight in kilograms. The intermediate results show your current BMI and the target BMI you set, along with the difference between your current and goal weight. A positive difference indicates weight loss is needed, while a negative difference suggests weight gain. The accompanying chart visually represents your current and target BMI relative to standard categories, and the table provides context for different BMI classifications.

Decision-Making Guidance

Your BMI goal weight is a guide, not a rigid rule. Use these results to inform your health decisions:

  • Set Realistic Goals: Aim for gradual and sustainable changes. Rapid weight loss or gain is often unhealthy.
  • Consult Professionals: Always discuss significant weight changes or health goals with a doctor or registered dietitian, especially if you have underlying health conditions.
  • Focus on Overall Health: Remember that weight is just one aspect of health. Combine weight management with a balanced diet, regular physical activity, and adequate sleep for the best outcomes.

Key Factors That Affect BMI Goal Weight Results

While the BMI goal weight calculator provides a mathematical target, several real-world factors can influence its applicability and how one achieves it:

  1. Body Composition (Muscle vs. Fat):

    BMI doesn't differentiate between muscle mass and fat mass. Muscle is denser than fat. A highly muscular individual might have a higher BMI and a higher calculated goal weight, even if they have a low body fat percentage. Relying solely on BMI goal weight might be misleading in such cases. Body fat percentage is often a better indicator of health.

  2. Age and Gender:

    Metabolism and body composition can change with age and differ between genders. While the BMI formula itself doesn't change, the 'ideal' BMI range or the ease of achieving a BMI goal weight might be influenced by these demographic factors. For instance, older adults might naturally carry less muscle mass.

  3. Bone Density and Frame Size:

    Individuals with larger bone structures might naturally weigh more, even if they are lean. A calculated BMI goal weight might seem low for someone with a naturally large frame, leading to an inaccurate perception of their health status based solely on BMI.

  4. Activity Level and Fitness Goals:

    Athletes or individuals engaged in intense physical training often have higher muscle mass. Their ideal weight might correspond to a higher BMI than the standard 'healthy' range. A BMI goal weight calculator may need to be adjusted or used alongside other metrics like lean body mass percentage.

  5. Underlying Health Conditions:

    Certain medical conditions (e.g., edema, certain hormonal imbalances, specific diseases) can affect body weight independently of diet and exercise. A BMI goal weight calculation should be considered in the context of overall health and medical advice. Medical professionals can help interpret results.

  6. Pregnancy and Lactation:

    BMI calculations and goal weights are not appropriate for pregnant or breastfeeding women due to physiological changes that significantly alter body weight and composition. Specialized guidance is required during these life stages.

  7. Genetics:

    Genetic predispositions can influence metabolism, fat distribution, and muscle-building potential. While a BMI goal weight provides a target, individual genetic factors can affect the path and pace towards achieving it.

  8. Dietary Habits and Nutrition:

    The quality of food consumed impacts health beyond just weight. Achieving a BMI goal weight through nutrient-poor foods might not lead to good health. A balanced diet rich in essential nutrients is crucial, regardless of the target weight.

Frequently Asked Questions (FAQ)

What is the healthy BMI range? The generally accepted healthy BMI range is from 18.5 to 24.9. Our BMI goal weight calculator uses this range as a common target. Can I have a healthy BMI but still be unhealthy? Yes. BMI doesn't measure body fat percentage or muscle mass. A person could have a 'healthy' BMI but a high body fat percentage and low muscle mass, indicating poor health. Conversely, a muscular person might have a high BMI but be very healthy. How quickly should I aim to reach my goal weight? Sustainable weight loss is typically recommended at 0.5 to 1 kg (1 to 2 lbs) per week. For weight gain, a gradual increase is also advised. Consult a healthcare provider for personalized advice. The BMI goal weight calculator provides the target, not the timeline. Does BMI account for height? Yes, the BMI calculation intrinsically accounts for height by dividing weight by the square of height. This ensures that taller individuals are not unfairly penalized for naturally weighing more. Our BMI goal weight calculator uses your specific height. What if my goal weight is considered underweight or overweight by BMI standards? Sometimes, medical conditions, specific athletic requirements, or body composition mean a person's ideal weight might fall outside the standard 'healthy' BMI range. Always consult a healthcare professional if your desired BMI goal weight deviates significantly from recommendations or if you have concerns. Can I use the calculator if I'm pregnant or breastfeeding? No. BMI and associated goal weight calculations are not suitable for pregnant or breastfeeding individuals due to significant physiological changes. Consult your doctor for appropriate guidance during these times. What's the difference between current BMI and goal weight? Current BMI is a snapshot of your weight status right now based on your current height and weight. Your BMI goal weight is a projected weight that would result in a specific, often healthier, BMI value for your given height. The difference highlights the amount of weight to adjust. Should I choose the lowest end of the healthy BMI range as my goal? Not necessarily. The healthy BMI range (18.5-24.9) is broad for a reason. Your ideal weight depends on many factors like body composition, genetics, and lifestyle. A BMI goal weight should be a target that feels achievable and promotes overall well-being, ideally chosen in consultation with a health professional.

Related Tools and Internal Resources

var chart = null; // Global variable for the chart instance function validateInput(value, id, errorId, min, max) { var errorElement = document.getElementById(errorId); errorElement.style.display = 'none'; // Hide previous error if (value === null || value === " || isNaN(parseFloat(value))) { errorElement.textContent = 'This field is required and must be a number.'; errorElement.style.display = 'block'; return false; } var numValue = parseFloat(value); if (numValue < 0) { errorElement.textContent = 'Value cannot be negative.'; errorElement.style.display = 'block'; return false; } if (id === 'desiredBmi' && numValue === 0) { errorElement.textContent = 'Desired BMI cannot be zero.'; errorElement.style.display = 'block'; return false; } if (min !== undefined && numValue max) { errorElement.textContent = 'Value must be no more than ' + max + '.'; errorElement.style.display = 'block'; return false; } return true; } function calculateBmiGoalWeight() { var heightCm = document.getElementById('height').value; var currentWeightKg = document.getElementById('currentWeight').value; var desiredBmiValue = document.getElementById('desiredBmi').value; // Clear previous errors document.getElementById('heightError').style.display = 'none'; document.getElementById('currentWeightError').style.display = 'none'; document.getElementById('desiredBmiError').style.display = 'none'; // Validate inputs var heightValid = validateInput(heightCm, 'height', 'heightError', 1); var currentWeightValid = validateInput(currentWeightKg, 'currentWeight', 'currentWeightError', 0); var desiredBmiValid = validateInput(desiredBmiValue, 'desiredBmi', 'desiredBmiError', 0.1); // BMI can technically be low, but 0 is invalid if (!heightValid || !currentWeightValid || !desiredBmiValid) { return; // Stop calculation if any input is invalid } var heightM = parseFloat(heightCm) / 100; var squaredHeightM = heightM * heightM; var currentBmi = parseFloat(currentWeightKg) / squaredHeightM; var goalWeight = parseFloat(desiredBmiValue) * squaredHeightM; var weightDifference = parseFloat(currentWeightKg) – goalWeight; // Update results display document.getElementById('currentBmiValue').textContent = currentBmi.toFixed(1); document.getElementById('targetBmiValue').textContent = parseFloat(desiredBmiValue).toFixed(1); document.getElementById('mainResult').textContent = goalWeight.toFixed(1) + ' kg'; document.getElementById('weightDiff').textContent = weightDifference.toFixed(1) + ' kg'; // Update chart updateBmiChart(currentBmi, parseFloat(desiredBmiValue)); } function resetCalculator() { document.getElementById('height').value = '170'; // Sensible default height document.getElementById('currentWeight').value = '75'; // Sensible default weight document.getElementById('desiredBmi').value = '22'; // Common healthy BMI // Clear errors document.getElementById('heightError').style.display = 'none'; document.getElementById('currentWeightError').style.display = 'none'; document.getElementById('desiredBmiError').style.display = 'none'; calculateBmiGoalWeight(); // Recalculate with defaults } function copyResults() { var mainResult = document.getElementById('mainResult').textContent; var currentBmi = document.getElementById('currentBmiValue').textContent; var targetBmi = document.getElementById('targetBmiValue').textContent; var weightDiff = document.getElementById('weightDiff').textContent; var height = document.getElementById('height').value; var currentWeight = document.getElementById('currentWeight').value; var desiredBmiInput = document.getElementById('desiredBmi').value; var textToCopy = "BMI Goal Weight Calculation:\n\n"; textToCopy += "Your Height: " + height + " cm\n"; textToCopy += "Your Current Weight: " + currentWeight + " kg\n"; textToCopy += "Desired BMI: " + desiredBmiInput + "\n\n"; textToCopy += "— Results —\n"; textToCopy += "Your Target Weight: " + mainResult + "\n"; textToCopy += "Current BMI: " + currentBmi + "\n"; textToCopy += "Desired BMI: " + targetBmi + "\n"; textToCopy += "Weight Difference: " + weightDiff + "\n\n"; textToCopy += "Key Assumption: Formula used is Goal Weight = Desired BMI × (Height in meters)²"; // Use navigator.clipboard for modern browsers, fallback for older ones if (navigator.clipboard && navigator.clipboard.writeText) { navigator.clipboard.writeText(textToCopy).then(function() { alert('Results copied to clipboard!'); }).catch(function(err) { console.error('Could not copy text: ', err); fallbackCopyTextToClipboard(textToCopy); }); } else { fallbackCopyTextToClipboard(textToCopy); } } function fallbackCopyTextToClipboard(text) { var textArea = document.createElement("textarea"); textArea.value = text; textArea.style.position = "fixed"; // Avoid scrolling to bottom textArea.style.left = "-9999px"; textArea.style.top = "-9999px"; document.body.appendChild(textArea); textArea.focus(); textArea.select(); try { var successful = document.execCommand('copy'); var msg = successful ? 'successful' : 'unsuccessful'; alert('Results copied to clipboard! (' + msg + ')'); } catch (err) { console.error('Oops, unable to copy', err); alert('Could not copy text. Please copy manually.'); } document.body.removeChild(textArea); } function updateBmiChart(currentBmi, desiredBmi) { var ctx = document.getElementById('bmiChart').getContext('2d'); // Destroy previous chart instance if it exists if (chart) { chart.destroy(); } var bmiCategories = ['Underweight', 'Healthy Weight', 'Overweight', 'Obese']; var bmiRanges = [18.5, 24.9, 29.9, 40]; // Upper bounds for categories var lowBmiValues = [0, 18.5, 25, 30]; // Lower bounds for categories var data = { labels: bmiCategories, datasets: [{ label: 'BMI Range', data: bmiRanges.map(function(upper, index) { var lower = lowBmiValues[index]; return [lower, upper]; // Represent ranges }), backgroundColor: [ 'rgba(255, 193, 7, 0.5)', // Underweight – Yellow 'rgba(40, 167, 69, 0.5)', // Healthy – Green 'rgba(255, 159, 64, 0.5)', // Overweight – Orange 'rgba(220, 53, 69, 0.5)' // Obese – Red ], borderColor: [ 'rgba(255, 193, 7, 1)', 'rgba(40, 167, 69, 1)', 'rgba(255, 159, 64, 1)', 'rgba(220, 53, 69, 1)' ], borderWidth: 1, categoryPercentage: 0.8, // Adjust bar width barPercentage: 0.8 }, { label: 'Your BMIs', data: [currentBmi, currentBmi, currentBmi, currentBmi].map(function(val, index) { if (val >= lowBmiValues[index] && val = lowBmiValues[index] && val <= bmiRanges[index]) return val; return null; }), backgroundColor: 'rgba(0, 123, 255, 0.8)', // Slightly different blue borderColor: 'rgba(0, 123, 255, 1)', borderWidth: 2, type: 'line', pointRadius: 6, pointHoverRadius: 8, borderDash: [5, 5] // Dashed line for target }] }; // Chart.js requires specific handling for bar ranges. For simplicity with pure canvas, // we'll plot the ranges as separate bars and use lines for individual points. // A more complex pure canvas approach would involve drawing rectangles for ranges. // Given constraints, we simulate range representation. // Using Chart.js for demonstration; if strictly pure canvas, this would need manual drawing. // Assuming Chart.js is available or can be included for this example. // If pure canvas (no libraries) is a MUST: manual drawing logic required here. // *** NOTE: This assumes Chart.js is available. If NOT, this section needs manual canvas drawing. *** // For this exercise, let's proceed assuming a charting library like Chart.js is intended // for the " element, or that pure SVG is an alternative. // Since pure SVG is allowed and potentially simpler without external libs: // Let's re-evaluate for pure SVG or pure Canvas drawing if Chart.js isn't allowed. // For a *pure* canvas solution without Chart.js: // We would need to manually draw rectangles for each BMI category and then lines/points for the BMIs. // This is significantly more complex to implement inline. // Given the constraint "Pure SVG () OR Native ", and "NO external chart libraries", // the " element implies drawing API usage. // Let's simplify and try to represent the ranges conceptually with pure canvas API for now. // This is a basic representation without complex libraries. var canvas = document.getElementById('bmiChart'); var ctx = canvas.getContext('2d'); canvas.width = canvas.offsetWidth; // Ensure canvas scales canvas.height = 300; ctx.clearRect(0, 0, canvas.width, canvas.height); // Clear previous drawings var chartHeight = canvas.height; var chartWidth = canvas.width; var padding = 40; var usableHeight = chartHeight – 2 * padding; var usableWidth = chartWidth – 2 * padding; var maxBmiValue = 45; // Consider a reasonable max for y-axis scale var yAxisScale = usableHeight / maxBmiValue; // Draw Axes ctx.beginPath(); ctx.moveTo(padding, padding); ctx.lineTo(padding, chartHeight – padding); // Y-axis ctx.lineTo(chartWidth – padding, chartHeight – padding); // X-axis ctx.strokeStyle = '#666'; ctx.lineWidth = 1; ctx.stroke(); // Y-Axis Labels and Ticks ctx.textAlign = 'right'; ctx.textBaseline = 'middle'; for (var i = 0; i <= maxBmiValue; i += 5) { ctx.fillText(i, padding – 5, chartHeight – padding – (i * yAxisScale)); ctx.beginPath(); ctx.moveTo(padding – 3, chartHeight – padding – (i * yAxisScale)); ctx.lineTo(padding, chartHeight – padding – (i * yAxisScale)); ctx.stroke(); } // X-Axis Labels (BMI Categories) ctx.textAlign = 'center'; ctx.textBaseline = 'top'; var numCategories = bmiCategories.length; var categoryWidth = usableWidth / numCategories; var categoryXPositions = []; for (var i = 0; i < numCategories; i++) { var xPos = padding + categoryWidth * (i + 0.5); ctx.fillText(bmiCategories[i], xPos, chartHeight – padding + 5); categoryXPositions.push(xPos); // Draw category boundaries ctx.beginPath(); ctx.moveTo(padding + categoryWidth * i, chartHeight – padding); ctx.lineTo(padding + categoryWidth * i, padding); ctx.setLineDash([2, 4]); ctx.strokeStyle = '#ccc'; ctx.stroke(); ctx.setLineDash([]); // Reset line dash } // Draw last boundary ctx.beginPath(); ctx.moveTo(chartWidth – padding, chartHeight – padding); ctx.lineTo(chartWidth – padding, padding); ctx.setLineDash([2, 4]); ctx.strokeStyle = '#ccc'; ctx.stroke(); ctx.setLineDash([]); // Draw BMI Ranges as colored rectangles ctx.globalAlpha = 0.4; // Transparency for ranges for (var i = 0; i < bmiCategories.length; i++) { var lower = lowBmiValues[i]; var upper = bmiRanges[i]; var color; switch (i) { case 0: color = '#FFC107'; break; // Underweight case 1: color = '#28A745'; break; // Healthy case 2: color = '#FF9800'; break; // Overweight case 3: color = '#DC3545'; break; // Obese default: color = '#ccc'; } ctx.fillStyle = color; var yStart = chartHeight – padding – (upper * yAxisScale); var rectHeight = (upper – lower) * yAxisScale; if (rectHeight < 0) rectHeight = 0; // Ensure height is not negative if upper maxBmiValue) rectHeight -= (upper – maxBmiValue) * yAxisScale; // Cap rect height if upper > maxBmiValue if (yStart < padding) yStart = padding; // Cap yStart ctx.fillRect(padding, yStart, usableWidth, rectHeight); } ctx.globalAlpha = 1; // Reset transparency // Draw Current BMI Line ctx.beginPath(); ctx.moveTo(padding, chartHeight – padding – (currentBmi * yAxisScale)); ctx.lineTo(chartWidth – padding, chartHeight – padding – (currentBmi * yAxisScale)); ctx.strokeStyle = '#004A99'; // Primary Blue ctx.lineWidth = 2; ctx.stroke(); // Draw Target BMI Line ctx.beginPath(); ctx.moveTo(padding, chartHeight – padding – (desiredBmi * yAxisScale)); ctx.lineTo(chartWidth – padding, chartHeight – padding – (desiredBmi * yAxisScale)); ctx.strokeStyle = '#007BFF'; // Slightly lighter blue ctx.lineWidth = 2; ctx.setLineDash([5, 5]); // Dashed line ctx.stroke(); ctx.setLineDash([]); // Reset line dash // Add legend outside canvas or infer from context. // For simplicity, labels are on the x-axis. } // Initial calculation and chart draw on page load window.onload = function() { calculateBmiGoalWeight(); // Ensure the chart is drawn correctly on load, accounting for potential resize // Small delay to ensure canvas is fully rendered and sized if dynamic setTimeout(function() { var currentBmi = parseFloat(document.getElementById('currentBmiValue').textContent); var desiredBmi = parseFloat(document.getElementById('targetBmiValue').textContent); // Check if values are valid numbers before drawing if (!isNaN(currentBmi) && !isNaN(desiredBmi)) { updateBmiChart(currentBmi, desiredBmi); } else { // If values are still '–', reset them before attempting to draw resetCalculator(); // Recalculate to set default values calculateBmiGoalWeight(); // Then draw chart with defaults var currentBmiAfterReset = parseFloat(document.getElementById('currentBmiValue').textContent); var desiredBmiAfterReset = parseFloat(document.getElementById('targetBmiValue').textContent); updateBmiChart(currentBmiAfterReset, desiredBmiAfterReset); } }, 100); }; // Recalculate on window resize to adjust chart window.addEventListener('resize', function() { // Recalculate first to ensure correct values are used for chart scaling calculateBmiGoalWeight(); // Use a small timeout to ensure layout shifts are complete before redrawing setTimeout(function() { var currentBmi = parseFloat(document.getElementById('currentBmiValue').textContent); var desiredBmi = parseFloat(document.getElementById('targetBmiValue').textContent); if (!isNaN(currentBmi) && !isNaN(desiredBmi)) { updateBmiChart(currentBmi, desiredBmi); } }, 100); });

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