Builtwithscience Com Calculator

BuiltWithScience Calorie & Macro Calculator

Use this calculator to estimate your Basal Metabolic Rate (BMR), Total Daily Energy Expenditure (TDEE), and a personalized calorie and macronutrient breakdown based on your body metrics and fitness goals, similar to the principles advocated by BuiltWithScience.com.

function calculateBuiltWithScience() { var age = parseFloat(document.getElementById("age").value); var gender = document.querySelector('input[name="gender"]:checked').value; var weightKg = parseFloat(document.getElementById("weightKg").value); var heightCm = parseFloat(document.getElementById("heightCm").value); var bodyFatPercent = parseFloat(document.getElementById("bodyFatPercent").value); var activityMultiplier = parseFloat(document.getElementById("activityLevel").value); var goal = document.getElementById("goal").value; var resultDiv = document.getElementById("result"); resultDiv.innerHTML = ""; // Clear previous results // Input validation if (isNaN(age) || age <= 0 || isNaN(weightKg) || weightKg <= 0 || isNaN(heightCm) || heightCm <= 0) { resultDiv.innerHTML = "Please enter valid positive numbers for Age, Weight, and Height."; return; } if (!isNaN(bodyFatPercent) && (bodyFatPercent 100)) { resultDiv.innerHTML = "Body Fat % must be between 0 and 100."; return; } var bmr; // Calculate BMR if (!isNaN(bodyFatPercent) && bodyFatPercent > 0 && bodyFatPercent < 100) { // Use Katch-McArdle if Body Fat % is provided and valid var leanBodyMassKg = weightKg * (1 – (bodyFatPercent / 100)); bmr = 370 + (21.6 * leanBodyMassKg); } else { // Use Mifflin-St Jeor if Body Fat % is not provided or invalid if (gender === "male") { bmr = (10 * weightKg) + (6.25 * heightCm) – (5 * age) + 5; } else { // female bmr = (10 * weightKg) + (6.25 * heightCm) – (5 * age) – 161; } } var tdee = bmr * activityMultiplier; var calorieGoal; var calorieAdjustment = 400; // Default adjustment for gain/loss if (goal === "maintain") { calorieGoal = tdee; } else if (goal === "lose") { calorieGoal = tdee – calorieAdjustment; } else { // gain calorieGoal = tdee + calorieAdjustment; } // Macro Calculation (BuiltWithScience style – high protein, moderate fat, remaining carbs) var proteinGramsPerKg = 2.2; // g/kg body weight var proteinGrams = proteinGramsPerKg * weightKg; var proteinCalories = proteinGrams * 4; var fatPercentageOfTotal = 0.25; // 25% of total calories from fat var fatCalories = calorieGoal * fatPercentageOfTotal; var fatGrams = fatCalories / 9; var remainingCalories = calorieGoal – proteinCalories – fatCalories; var carbGrams = remainingCalories / 4; var carbCalories = carbGrams * 4; // Ensure no negative macros if calorie goal is very low if (proteinGrams < 0) proteinGrams = 0; if (proteinCalories < 0) proteinCalories = 0; if (fatGrams < 0) fatGrams = 0; if (fatCalories < 0) fatCalories = 0; if (carbGrams < 0) carbGrams = 0; if (carbCalories < 0) carbCalories = 0; resultDiv.innerHTML = "

Your Estimated Metrics:

" + "Basal Metabolic Rate (BMR): " + bmr.toFixed(0) + " calories/day" + "Total Daily Energy Expenditure (TDEE): " + tdee.toFixed(0) + " calories/day" + "Daily Calorie Goal: " + calorieGoal.toFixed(0) + " calories/day" + "

Macronutrient Breakdown:

" + "Protein: " + proteinGrams.toFixed(0) + "g (" + proteinCalories.toFixed(0) + " calories)" + "Fat: " + fatGrams.toFixed(0) + "g (" + fatCalories.toFixed(0) + " calories)" + "Carbohydrates: " + carbGrams.toFixed(0) + "g (" + carbCalories.toFixed(0) + " calories)" + "Note: These are estimates. Individual needs may vary based on genetics, training intensity, and other factors."; } .builtwithscience-calculator-wrapper { font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif; max-width: 700px; margin: 20px auto; padding: 25px; background-color: #f9f9f9; border-radius: 10px; box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1); border: 1px solid #e0e0e0; } .builtwithscience-calculator-wrapper h2 { color: #2c3e50; text-align: center; margin-bottom: 20px; font-size: 1.8em; } .builtwithscience-calculator-wrapper p { color: #555; line-height: 1.6; margin-bottom: 15px; } .calculator-form .form-group { margin-bottom: 18px; display: flex; flex-direction: column; } .calculator-form label { font-weight: bold; margin-bottom: 8px; color: #34495e; font-size: 0.95em; } .calculator-form input[type="number"], .calculator-form select { width: 100%; padding: 12px; border: 1px solid #ccc; border-radius: 6px; box-sizing: border-box; font-size: 1em; color: #333; background-color: #fff; transition: border-color 0.3s ease; } .calculator-form input[type="number"]:focus, .calculator-form select:focus { border-color: #007bff; outline: none; box-shadow: 0 0 0 3px rgba(0, 123, 255, 0.25); } .calculator-form input[type="radio"] { margin-right: 5px; margin-left: 15px; } .calculator-form input[type="radio"] + label { font-weight: normal; margin-bottom: 0; display: inline-block; margin-right: 10px; } .calculator-form button { display: block; width: 100%; padding: 14px 20px; background-color: #007bff; color: white; border: none; border-radius: 6px; font-size: 1.1em; font-weight: bold; cursor: pointer; transition: background-color 0.3s ease, transform 0.2s ease; margin-top: 25px; } .calculator-form button:hover { background-color: #0056b3; transform: translateY(-2px); } .calculator-result { margin-top: 30px; padding: 20px; background-color: #e9f7ef; border: 1px solid #d4edda; border-radius: 8px; color: #155724; } .calculator-result h3 { color: #28a745; margin-top: 0; margin-bottom: 15px; font-size: 1.5em; border-bottom: 1px solid #d4edda; padding-bottom: 10px; } .calculator-result p { margin-bottom: 10px; font-size: 1.05em; } .calculator-result p strong { color: #000; } .calculator-result .error { color: #dc3545; font-weight: bold; background-color: #f8d7da; border: 1px solid #f5c6cb; padding: 10px; border-radius: 5px; } .calculator-result .note { font-size: 0.9em; color: #6c757d; margin-top: 20px; border-top: 1px dashed #ced4da; padding-top: 15px; }

Understanding Your Calorie & Macro Results

This calculator provides estimates for your Basal Metabolic Rate (BMR), Total Daily Energy Expenditure (TDEE), and a macronutrient breakdown, aligning with common fitness principles for body recomposition and muscle growth.

Basal Metabolic Rate (BMR)

Your BMR is the number of calories your body burns at rest to maintain basic life-sustaining functions like breathing, circulation, and cell production. It's the minimum energy required to keep you alive.

• Mifflin-St Jeor Equation: Used when body fat percentage is not provided. It's a widely accepted formula that considers age, gender, weight, and height.
• Katch-McArdle Formula: Used when your body fat percentage is entered. This formula is often considered more accurate for individuals with a known body fat percentage as it calculates BMR based on lean body mass, which is metabolically more active than fat mass.

Total Daily Energy Expenditure (TDEE)

Your TDEE is the total number of calories your body burns in a 24-hour period, including your BMR plus the calories burned through physical activity and the thermic effect of food. It represents the calories you need to consume to maintain your current weight.

The activity multipliers used are:

• Sedentary: Little or 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/week.
• Extremely Active: Hard daily exercise/physical job.

Daily Calorie Goal

Based on your TDEE and chosen goal:

• Maintain Weight: Your calorie goal is approximately equal to your TDEE.
• Lose Weight: A deficit of around 400 calories from your TDEE is applied to promote fat loss.
• Gain Weight: A surplus of around 400 calories from your TDEE is applied to support muscle growth.

These adjustments are general guidelines. For more aggressive or conservative goals, you might adjust your intake further.

Macronutrient Breakdown

Macronutrients (protein, fats, and carbohydrates) are essential for energy, growth, and repair. This calculator provides a breakdown based on common recommendations for fitness enthusiasts:

• Protein: Calculated at approximately 2.2 grams per kilogram of body weight. Protein is crucial for muscle repair, growth, and satiety.
• Fats: Set at 25% of your total daily calorie goal. Fats are vital for hormone production, nutrient absorption, and overall health.
• Carbohydrates: The remaining calories after protein and fat are allocated to carbohydrates. Carbs are your body's primary energy source, fueling workouts and daily activities.

Remember, these calculations are estimates. Factors like individual metabolism, training intensity, sleep, and stress can influence your actual caloric and macronutrient needs. It's always recommended to monitor your progress and adjust your intake as needed.