How to Calculate Protein Based on Weight

How to Calculate Protein Based on Weight | Daily Intake Calculator :root { –primary-color: #004a99; –success-color: #28a745; –background-color: #f8f9fa; –text-color: #333; –border-color: #ccc; –card-background: #ffffff; –shadow: 0 2px 5px rgba(0,0,0,0.1); } body { font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif; background-color: var(–background-color); color: var(–text-color); line-height: 1.6; margin: 0; padding: 20px; } .container { max-width: 960px; margin: 0 auto; background-color: var(–card-background); padding: 30px; border-radius: 8px; box-shadow: var(–shadow); } h1, h2, h3 { color: var(–primary-color); text-align: center; margin-bottom: 20px; } h1 { font-size: 2.5em; } h2 { font-size: 1.8em; margin-top: 40px; border-bottom: 2px solid var(–primary-color); padding-bottom: 5px; } h3 { font-size: 1.4em; margin-top: 30px; } .calculator-section { background-color: var(–card-background); padding: 25px; border-radius: 8px; box-shadow: var(–shadow); margin-bottom: 40px; } .loan-calc-container { display: flex; flex-direction: column; gap: 15px; } .input-group { display: flex; flex-direction: column; gap: 5px; } .input-group label { font-weight: bold; font-size: 1.1em; color: var(–primary-color); } .input-group input[type="number"], .input-group select { padding: 12px; border: 1px solid var(–border-color); border-radius: 5px; font-size: 1em; width: 100%; box-sizing: border-box; } .input-group input[type="number"]:focus, .input-group select:focus { border-color: var(–primary-color); outline: none; box-shadow: 0 0 0 2px rgba(0, 74, 153, 0.2); } .input-group .helper-text { font-size: 0.9em; color: #666; margin-top: 5px; } .input-group .error-message { color: red; font-size: 0.85em; margin-top: 5px; display: none; /* Hidden by default */ } .button-group { display: flex; gap: 10px; margin-top: 20px; flex-wrap: wrap; } button { padding: 12px 20px; border: none; border-radius: 5px; cursor: pointer; font-size: 1.1em; font-weight: bold; transition: background-color 0.3s ease; } .btn-primary { background-color: var(–primary-color); color: white; } .btn-primary:hover { background-color: #003366; } .btn-secondary { background-color: var(–success-color); color: white; } .btn-secondary:hover { background-color: #218838; } .btn-reset { background-color: #6c757d; color: white; } .btn-reset:hover { background-color: #5a6268; } #results { background-color: var(–primary-color); color: white; padding: 20px; border-radius: 8px; margin-top: 25px; box-shadow: var(–shadow); text-align: center; } #results h3 { color: white; margin-bottom: 15px; } .result-value { font-size: 2em; font-weight: bold; margin-bottom: 5px; } .result-label { font-size: 1.1em; opacity: 0.9; } .intermediate-results div, .formula-explanation { margin-top: 15px; font-size: 0.95em; padding: 10px; background-color: rgba(0, 74, 153, 0.1); border-left: 3px solid var(–primary-color); border-radius: 3px; } .formula-explanation strong { color: var(–primary-color); } table { width: 100%; border-collapse: collapse; margin-top: 20px; background-color: var(–card-background); box-shadow: var(–shadow); border-radius: 8px; overflow: hidden; /* For rounded corners on cells */ } th, td { padding: 12px 15px; text-align: left; border-bottom: 1px solid var(–border-color); } thead th { background-color: var(–primary-color); color: white; font-weight: bold; } tbody tr:nth-child(even) { background-color: #f2f2f2; } tbody tr:hover { background-color: #e9ecef; } caption { caption-side: top; text-align: left; font-weight: bold; color: var(–primary-color); margin-bottom: 10px; font-size: 1.2em; } .chart-container { text-align: center; margin-top: 30px; background-color: var(–card-background); padding: 20px; border-radius: 8px; box-shadow: var(–shadow); } canvas { max-width: 100%; height: auto !important; /* Ensure canvas scales correctly */ } .chart-legend { margin-top: 10px; font-size: 0.9em; color: #555; } .chart-legend span { display: inline-block; margin: 0 10px; } .chart-legend .legend-item { display: inline-flex; align-items: center; margin: 0 8px; } .chart-legend .legend-color-box { display: inline-block; width: 15px; height: 15px; margin-right: 5px; border: 1px solid #999; } .article-content { background-color: var(–card-background); padding: 30px; border-radius: 8px; box-shadow: var(–shadow); margin-top: 40px; } .article-content p, .article-content ul, .article-content ol { margin-bottom: 15px; } .article-content a { color: var(–primary-color); text-decoration: none; } .article-content a:hover { text-decoration: underline; } .faq-item { margin-bottom: 15px; } .faq-item strong { color: var(–primary-color); display: block; font-size: 1.1em; margin-bottom: 5px; } .internal-links-section ul { list-style: none; padding: 0; } .internal-links-section li { margin-bottom: 10px; } @media (min-width: 600px) { .container { padding: 40px; } h1 { font-size: 3em; } .button-group { flex-wrap: nowrap; /* Prevent wrapping on larger screens */ } }

How to Calculate Protein Based on Weight

Your Essential Guide to Daily Protein Intake

Daily Protein Intake Calculator

Enter your weight in kilograms (kg).
Sedentary (little to no exercise) Lightly Active (light exercise/sports 1-3 days/week) Moderately Active (moderate exercise/sports 3-5 days/week) Very Active (hard exercise/sports 6-7 days a week) Extra Active (very hard exercise/sports & physical job)
Choose the option that best describes your typical physical activity.
Maintain Muscle Mass Build Muscle Mass Lose Fat (while preserving muscle)
Select your primary fitness objective.

Your Daily Protein Needs

— g
grams per day
Recommendation Range: — to — g/day
Protein per kg: — g/kg
Protein per lb: — g/lb
Formula Used: Your daily protein intake is calculated based on your body weight and a recommended protein multiplier (grams per kilogram of body weight) that varies depending on your activity level and fitness goal. This multiplier typically ranges from 1.2 g/kg for sedentary individuals aiming to maintain, up to 2.2 g/kg for those actively building muscle or in a caloric deficit.

Understanding Protein Intake

Sedentary Lightly Active Moderately Active Very Active Extra Active
Protein Intake Recommendations by Activity Level & Goal (per kg of body weight)

Protein Intake Benchmarks Table

Recommended Daily Protein Intake Multipliers (g/kg)
Activity Level / Goal Maintain Muscle Build Muscle Lose Fat
Sedentary 1.2 – 1.5 1.5 – 1.8 1.4 – 1.7
Lightly Active 1.3 – 1.6 1.6 – 1.9 1.5 – 1.8
Moderately Active 1.4 – 1.7 1.7 – 2.0 1.6 – 1.9
Very Active 1.5 – 1.8 1.8 – 2.1 1.7 – 2.0
Extra Active 1.6 – 2.0 1.9 – 2.2 1.8 – 2.2

What is Daily Protein Intake?

Daily protein intake refers to the total amount of protein an individual consumes within a 24-hour period. Protein is one of the three macronutrients (along with carbohydrates and fats) essential for human health. It plays a critical role in building and repairing tissues, producing enzymes and hormones, and supporting immune function. Understanding how to calculate your optimal daily protein intake is crucial for anyone looking to manage their weight, build muscle, enhance athletic performance, or simply maintain good health.

Who should use it? Anyone interested in optimizing their nutrition for fitness, health, or weight management should pay attention to their daily protein intake. This includes athletes, bodybuilders, individuals trying to lose weight, older adults looking to preserve muscle mass, and even those with generally active lifestyles. Getting the right amount of protein can significantly impact body composition, recovery, and overall well-being.

Common misconceptions about protein intake include the idea that more is always better, which can lead to unnecessary strain on the kidneys or displacement of other essential nutrients. Another misconception is that only bodybuilders need high protein, when in fact, moderate protein intake is beneficial for most people. The specific requirements are highly individualized.

How to Calculate Protein Based on Weight: Formula and Explanation

The fundamental method for how to calculate protein based on weight involves multiplying your body weight by a specific factor that accounts for your activity level and fitness goals. This factor is typically expressed in grams of protein per kilogram of body weight (g/kg).

The Core Formula:

Daily Protein Intake (grams) = Body Weight (kg) × Protein Factor (g/kg)

Variable Explanations:

  • Body Weight (kg): This is your current weight measured in kilograms. If you measure your weight in pounds, you'll need to convert it first (1 lb ≈ 0.453592 kg).
  • Protein Factor (g/kg): This is the multiplier that dictates your protein needs. It's not a fixed number but rather a range determined by several factors.

Variable Table:

Protein Intake Variables
Variable Meaning Unit Typical Range
Body Weight Your current mass. Kilograms (kg) / Pounds (lb) Varies per individual
Protein Factor Recommended daily protein intake per unit of body weight, adjusted for activity and goals. Grams per Kilogram (g/kg) 1.2 – 2.2

Derivation of the Protein Factor:

The recommended Protein Factor (g/kg) is derived from research and guidelines established by health and sports science organizations. These guidelines consider the body's requirements for muscle protein synthesis, repair, and other metabolic processes. The general consensus is:

  • Sedentary Individuals: Need less protein, typically around 1.2-1.5 g/kg, mainly for basic bodily functions and tissue maintenance.
  • Lightly Active Individuals: Require slightly more to support occasional exercise, around 1.3-1.6 g/kg.
  • Moderately Active Individuals: Need more to aid recovery and muscle repair from regular workouts, usually 1.4-1.7 g/kg.
  • Very Active Individuals: Higher demands for muscle repair and growth, ranging from 1.5-1.8 g/kg.
  • Individuals Building Muscle: Protein needs are higher to facilitate muscle hypertrophy, often in the 1.6-2.2 g/kg range.
  • Individuals Losing Fat: Higher protein intake (1.8-2.2 g/kg) helps preserve lean muscle mass during a calorie deficit and increases satiety.

Our calculator uses these ranges to provide a specific target based on your selection. For instance, a 70kg person aiming to build muscle might aim for 1.8 g/kg, resulting in 70kg * 1.8 g/kg = 126 grams of protein per day.

Practical Examples (Real-World Use Cases)

Let's illustrate how to calculate protein based on weight with practical scenarios:

Example 1: Muscle Gain Focus

Scenario: Sarah is 65 kg, moderately active (exercises 4 times a week), and her primary goal is to build muscle mass.

Inputs:

  • Weight: 65 kg
  • Activity Level: Moderately Active
  • Fitness Goal: Build Muscle Mass

Calculation: Using the calculator, Sarah selects 'Moderately Active' and 'Build Muscle Mass'. The calculator suggests a protein factor of approximately 1.8 g/kg.

Result: Daily Protein Intake = 65 kg × 1.8 g/kg = 117 grams of protein per day.

Interpretation: Sarah should aim to consume around 117 grams of protein daily to support her muscle-building goals, ensuring adequate protein for muscle repair and synthesis.

Example 2: Fat Loss Support

Scenario: Mark weighs 90 kg, is very active (trains 6 days a week), and his goal is to lose fat while preserving muscle.

Inputs:

  • Weight: 90 kg
  • Activity Level: Very Active
  • Fitness Goal: Lose Fat (while preserving muscle)

Calculation: Mark inputs his details. The calculator recommends a higher protein factor for fat loss and high activity, around 2.0 g/kg.

Result: Daily Protein Intake = 90 kg × 2.0 g/kg = 180 grams of protein per day.

Interpretation: Mark's high protein intake of 180 grams per day will help him feel fuller, preserve hard-earned muscle mass during his calorie deficit, and support his metabolic rate.

How to Use This Protein Calculator

Our calculator is designed for simplicity and accuracy. Follow these steps:

  1. Enter Your Weight: Input your current body weight in kilograms (kg) into the 'Your Body Weight' field. If you know your weight in pounds, divide it by 2.205 to get kilograms.
  2. Select Activity Level: Choose the option from the dropdown that best describes your average weekly physical activity. Be honest to get the most accurate recommendation.
  3. Choose Your Goal: Select whether your primary objective is to maintain muscle, build muscle, or lose fat.
  4. Calculate: Click the 'Calculate Protein' button.

Reading and Using the Results:

  • Main Result: The largest number displayed is your target daily protein intake in grams.
  • Recommendation Range: This shows the minimum and maximum recommended protein intake based on standard guidelines for your inputs. Aiming within this range is beneficial.
  • Protein per kg/lb: These values show the specific multiplier (g/kg) and its equivalent in grams per pound (g/lb) used for your calculation, offering insight into the underlying recommendation.
  • Formula Explanation: Provides a brief overview of how the calculation is performed.

Decision-Making Guidance:

Use the calculated number as a target for your daily protein consumption. Distribute this intake across your meals throughout the day. Adjust your diet by incorporating protein-rich foods such as lean meats, poultry, fish, eggs, dairy, legumes, tofu, and protein supplements if needed. Consulting a nutritionist or registered dietitian can provide personalized advice.

Key Factors That Affect Protein Needs

While body weight is the primary factor in how to calculate protein based on weight, several other elements influence your specific requirements:

  1. Activity Intensity and Duration: More intense and prolonged exercise sessions increase muscle breakdown and therefore protein needs for repair and growth.
  2. Muscle Mass: Individuals with higher muscle mass generally require more protein to maintain it, especially during calorie restriction.
  3. Age: Protein needs may increase with age to combat sarcopenia (age-related muscle loss). Older adults often benefit from higher protein intakes than previously recommended.
  4. Caloric Intake: When in a calorie deficit for fat loss, protein needs increase significantly (often to the higher end of the g/kg range) to prevent muscle catabolism.
  5. Health Status and Injury: Illness, surgery, or significant injury can dramatically increase protein requirements for tissue repair and immune response.
  6. Dietary Protein Quality: Complete proteins (like animal sources and soy) contain all essential amino acids, while incomplete proteins (most plant sources) may need to be combined to provide a full amino acid profile.
  7. Training Goals: Whether your goal is strength gain, endurance improvement, or hypertrophy, the specific training adaptations desired will influence protein utilization.

Frequently Asked Questions (FAQ)

Q1: Is it possible to consume too much protein?

A: While generally safe for healthy individuals, excessively high protein intake over extended periods could potentially strain the kidneys or lead to dehydration. It can also displace other vital nutrients if not balanced. Sticking to recommended ranges is advisable.

Q2: Should I calculate protein based on my ideal weight or current weight?

A: It's generally best to base calculations on your current weight. If you are significantly overweight, some professionals suggest using a slightly adjusted weight or lean body mass for calculation, but for most, current weight is the standard starting point.

Q3: Do I need to eat protein every few hours?

A: While spreading protein intake throughout the day can optimize muscle protein synthesis, the total daily intake is the most critical factor for overall goals. Consistent daily intake is more important than rigid timing for most individuals.

Q4: What are good sources of protein?

A: Excellent sources include chicken breast, turkey, lean beef, fish (salmon, tuna), eggs, Greek yogurt, cottage cheese, milk, tofu, tempeh, lentils, beans, and protein powders (whey, casein, soy, pea).

Q5: How does protein help with weight loss?

A: Protein has a higher thermic effect than carbs or fats, meaning your body burns more calories digesting it. It also increases satiety, helping you feel fuller for longer, and is crucial for preserving muscle mass during a calorie deficit, which helps maintain metabolism.

Q6: Should vegetarians and vegans calculate protein differently?

A: The basic formula (weight x factor) still applies. However, plant-based proteins can sometimes be less bioavailable or lack certain essential amino acids. Vegetarians and vegans may aim for the higher end of the recommended ranges and focus on consuming a variety of plant protein sources to ensure a complete amino acid profile.

Q7: What if my activity level fluctuates?

A: Use an average of your activity level over the week. On rest days, your protein needs are slightly lower, but the higher needs on training days typically balance this out. Prioritize consistency.

Q8: Does the calculator account for protein powders?

A: The calculator provides a target gram amount. You can meet this target using whole foods, protein powders, or a combination of both. Protein powders are a convenient way to supplement intake, especially around workouts or if dietary intake is insufficient.

var weightInput = document.getElementById('weight'); var activityLevelSelect = document.getElementById('activityLevel'); var goalSelect = document.getElementById('goal'); var mainResultDiv = document.getElementById('mainResult'); var recommendationRangeDiv = document.getElementById('recommendationRange'); var gPerKgDiv = document.getElementById('gPerKg'); var gPerLbDiv = document.getElementById('gPerLb'); var weightErrorDiv = document.getElementById('weightError'); var chartInstance = null; // To hold chart instance function validateInput(inputId, errorElementId, min, max) { var input = document.getElementById(inputId); var errorElement = document.getElementById(errorElementId); var value = parseFloat(input.value); if (isNaN(value) || value <= 0) { errorElement.textContent = "Please enter a valid positive number."; errorElement.style.display = 'block'; input.style.borderColor = 'red'; return false; } else if (min !== undefined && max !== undefined && (value max)) { errorElement.textContent = "Value must be between " + min + " and " + max + "."; errorElement.style.display = 'block'; input.style.borderColor = 'red'; return false; } else { errorElement.textContent = "; errorElement.style.display = 'none'; input.style.borderColor = 'var(–border-color)'; return true; } } function getProteinFactor(activity, goal) { var factor = 1.2; // Default baseline var factors = { sedentary: { maintain: 1.3, build: 1.5, lose: 1.4 }, lightly_active: { maintain: 1.4, build: 1.7, lose: 1.6 }, moderately_active: { maintain: 1.5, build: 1.9, lose: 1.7 }, very_active: { maintain: 1.6, build: 2.1, lose: 1.9 }, extra_active: { maintain: 1.8, build: 2.2, lose: 2.0 } }; if (factors[activity] && factors[activity][goal]) { factor = factors[activity][goal]; } return factor; } function calculateProtein() { var isValidWeight = validateInput('weight', 'weightError'); if (!isValidWeight) { mainResultDiv.textContent = '– g'; recommendationRangeDiv.innerHTML = 'Recommendation Range: — to — g/day'; gPerKgDiv.innerHTML = 'Protein per kg: — g/kg'; gPerLbDiv.innerHTML = 'Protein per lb: — g/lb'; updateChart(0, 0, 0, 0, 0); // Reset chart return; } var weight = parseFloat(weightInput.value); var activity = activityLevelSelect.value; var goal = goalSelect.value; var proteinFactor = getProteinFactor(activity, goal); var proteinPerKg = parseFloat(proteinFactor.toFixed(1)); var proteinPerLb = parseFloat((proteinPerKg * 0.453592).toFixed(1)); // Convert g/kg to g/lb var mainResult = parseFloat((weight * proteinPerKg).toFixed(0)); // Calculate range based on typical min/max for the selected category var minFactor = 1.2, maxFactor = 2.2; if (activity === 'sedentary') { minFactor = 1.2; maxFactor = 1.8; } else if (activity === 'lightly_active') { minFactor = 1.3; maxFactor = 1.9; } else if (activity === 'moderately_active') { minFactor = 1.4; maxFactor = 2.0; } else if (activity === 'very_active') { minFactor = 1.5; maxFactor = 2.1; } else if (activity === 'extra_active') { minFactor = 1.6; maxFactor = 2.2; } // Adjust range for specific goals if (goal === 'build') { minFactor = Math.max(minFactor, 1.6); maxFactor = Math.min(maxFactor, 2.2); } else if (goal === 'lose') { minFactor = Math.max(minFactor, 1.8); maxFactor = Math.min(maxFactor, 2.2); } else { // maintain minFactor = Math.max(minFactor, 1.2); maxFactor = Math.min(maxFactor, 1.8); } var lowerBound = parseFloat((weight * minFactor).toFixed(0)); var upperBound = parseFloat((weight * maxFactor).toFixed(0)); mainResultDiv.textContent = mainResult + ' g'; recommendationRangeDiv.innerHTML = 'Recommendation Range: ' + lowerBound + ' to ' + upperBound + ' g/day'; gPerKgDiv.innerHTML = 'Protein per kg: ' + proteinPerKg + ' g/kg'; gPerLbDiv.innerHTML = 'Protein per lb: ' + proteinPerLb + ' g/lb'; updateChart(weight, proteinPerKg, minFactor, maxFactor, activity); // Update chart with relevant data } function resetCalculator() { weightInput.value = '70'; // Sensible default activityLevelSelect.value = 'moderately_active'; goalSelect.value = 'maintain'; weightErrorDiv.textContent = "; weightErrorDiv.style.display = 'none'; weightInput.style.borderColor = 'var(–border-color)'; calculateProtein(); // Recalculate with defaults } function copyResults() { var mainResultText = mainResultDiv.textContent; var rangeText = recommendationRangeDiv.textContent.replace('', ").replace('', "); var gPerKgText = gPerKgDiv.textContent.replace('', ").replace('', "); var gPerLbText = gPerLbDiv.textContent.replace('', ").replace('', "); var activity = activityLevelSelect.options[activityLevelSelect.selectedIndex].text; var goal = goalSelect.options[goalSelect.selectedIndex].text; var textToCopy = "— Daily Protein Intake Results —\n\n"; textToCopy += "Primary Target: " + mainResultText + "\n"; textToCopy += rangeText + "\n"; textToCopy += gPerKgText + "\n"; textToCopy += gPerLbText + "\n\n"; textToCopy += "Assumptions:\n"; textToCopy += "- Activity Level: " + activity + "\n"; textToCopy += "- Fitness Goal: " + goal + "\n"; textToCopy += "- Weight Basis: " + parseFloat(weightInput.value) + " kg\n"; if (navigator.clipboard && window.isSecureContext) { 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"; 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('Fallback: Oops, unable to copy', err); alert('Failed to copy results. Please copy manually.'); } document.body.removeChild(textArea); } function updateChart(weight, proteinPerKg, minFactor, maxFactor, currentActivity) { var ctx = document.getElementById('proteinChart').getContext('2d'); // Define factors for each activity level and goal var chartData = { labels: ["Sedentary", "Lightly Active", "Moderately Active", "Very Active", "Extra Active"], datasets: [ { label: 'Maintain Muscle (g/kg)', data: [1.3, 1.4, 1.5, 1.6, 1.8], // Min values for maintain borderColor: '#004a99', backgroundColor: 'rgba(0, 74, 153, 0.2)', fill: false, pointRadius: 5, pointHoverRadius: 7 }, { label: 'Build Muscle (g/kg)', data: [1.5, 1.7, 1.9, 2.1, 2.2], // Mid/high values for build borderColor: '#ffc107', backgroundColor: 'rgba(255, 193, 7, 0.2)', fill: false, pointRadius: 5, pointHoverRadius: 7 }, { label: 'Lose Fat (g/kg)', data: [1.4, 1.6, 1.7, 1.9, 2.0], // High values for lose borderColor: '#dc3545', backgroundColor: 'rgba(220, 53, 69, 0.2)', fill: false, pointRadius: 5, pointHoverRadius: 7 } ] }; // Find the index of the currently selected activity level var activityIndexMap = { sedentary: 0, lightly_active: 1, moderately_active: 2, very_active: 3, extra_active: 4 }; var currentActivityIndex = activityIndexMap[currentActivity] !== undefined ? activityIndexMap[currentActivity] : 2; // Default to moderately active // Highlight the point for the selected activity level and goal chartData.datasets.forEach(function(dataset) { dataset.pointBackgroundColor = []; for (var i = 0; i < chartData.labels.length; i++) { if (i === currentActivityIndex) { // Check if the current factor falls within the dataset's implied range for the goal var currentFactor = parseFloat(dataset.data[i]); var goalType = dataset.label.split(' ')[0].toLowerCase(); // 'maintain', 'build', 'lose' var selectedGoal = goalSelect.value; var isMatch = false; if (goalType === 'maintain' && selectedGoal === 'maintain') isMatch = true; if (goalType === 'build' && selectedGoal === 'build') isMatch = true; if (goalType === 'lose' && selectedGoal === 'lose') isMatch = true; if (isMatch) { dataset.pointBackgroundColor.push('yellow'); // Highlight color } else { dataset.pointBackgroundColor.push('rgba(0,0,0,0.5)'); } } else { dataset.pointBackgroundColor.push('rgba(0,0,0,0.5)'); } } }); var options = { responsive: true, maintainAspectRatio: false, scales: { y: { beginAtZero: true, title: { display: true, text: 'Grams of Protein per Kilogram of Body Weight (g/kg)' }, suggestedMax: 2.5 // Ensure enough space }, x: { title: { display: true, text: 'Activity Level' } } }, plugins: { tooltip: { callbacks: { label: function(context) { var label = context.dataset.label || ''; if (label) { label += ': '; } if (context.parsed.y !== null) { label += context.parsed.y + ' g/kg'; } label += '\n(Weight: ' + weight + ' kg)'; // Add weight context return label; } } } } }; if (chartInstance) { chartInstance.destroy(); } chartInstance = new Chart(ctx, { type: 'line', data: chartData, options: options }); } // Initial calculation and chart rendering on page load document.addEventListener('DOMContentLoaded', function() { resetCalculator(); // Set defaults and calculate updateChart(parseFloat(weightInput.value), 1.5, 1.2, 2.2, activityLevelSelect.value); // Initial chart draw }); // Add event listeners for real-time updates (optional, but good UX) weightInput.addEventListener('input', calculateProtein); activityLevelSelect.addEventListener('change', calculateProtein); goalSelect.addEventListener('change', calculateProtein);

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