Sedentary (little or no exercise)
Lightly Active (exercise 1-3 days/week)
Moderately Active (exercise 3-5 days/week)
Very Active (exercise 6-7 days/week)
Extra Active (very intense exercise daily, or physical job)
Your Daily Calorie Target for Weight Loss:
— kcal
Understanding Your Calorie Needs for Weight Loss
Losing weight effectively and sustainably relies on creating a calorie deficit. This means consuming fewer calories than your body burns. This calculator helps you estimate your daily calorie needs to achieve a specific weekly weight loss goal.
The Math Behind the Calculator:
The calculator uses the Mifflin-St Jeor equation to estimate your Basal Metabolic Rate (BMR), which is the number of calories your body burns at rest. Then, it adjusts this for your activity level to determine your Total Daily Energy Expenditure (TDEE).
Basal Metabolic Rate (BMR):
For Men: BMR = (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) + 5
For Women: BMR = (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) – 161
Total Daily Energy Expenditure (TDEE): TDEE = BMR × Activity Level Factor
Calorie Deficit for Weight Loss: To lose weight, you need to consume fewer calories than your TDEE. A common and healthy rate of weight loss is 0.5 kg to 1 kg per week. Since 1 kg of fat is approximately equivalent to 7,700 calories, a deficit of 500-1000 calories per day generally leads to a weight loss of 0.5-1 kg per week.
*(Note: 7700 kcal / 7 days ≈ 1100 kcal/day deficit for 1kg/week loss)*
How to Use the Calculator:
Enter Your Current Stats: Input your current weight in kilograms, height in centimeters, age in years, and select your gender.
Select Your Activity Level: Choose the option that best describes your typical weekly physical activity.
Set Your Weight Loss Goal: Specify how many kilograms you aim to lose per week (e.g., 0.5 kg for a sustainable loss, 1 kg for a more aggressive approach).
Calculate: Click the "Calculate Target Calories" button.
Interpreting the Results:
The calculator will provide your estimated daily calorie intake needed to achieve your desired weekly weight loss. It's crucial to remember that this is an estimate. Individual metabolisms can vary. Listen to your body, adjust your intake as needed, and focus on nutrient-dense foods.
Important Considerations:
Sustainability: Aiming for a loss of 0.5 kg to 1 kg per week is generally considered healthy and sustainable. Rapid weight loss can be difficult to maintain and may not be healthy.
Nutrition Quality: Focus on a balanced diet rich in fruits, vegetables, lean proteins, and whole grains, rather than just calorie counting.
Exercise: Incorporating regular physical activity not only burns calories but also improves overall health, muscle mass, and metabolism.
Consult Professionals: For personalized advice, especially if you have underlying health conditions, consult a doctor or a registered dietitian.
function calculateCalories() {
var weight = parseFloat(document.getElementById("weight").value);
var height = parseFloat(document.getElementById("height").value);
var age = parseFloat(document.getElementById("age").value);
var gender = document.getElementById("gender").value;
var activityLevel = parseFloat(document.getElementById("activityLevel").value);
var weightLossGoal = parseFloat(document.getElementById("weightLossGoal").value);
var resultValueElement = document.getElementById("result-value");
// Input validation
if (isNaN(weight) || weight <= 0 ||
isNaN(height) || height <= 0 ||
isNaN(age) || age <= 0 ||
isNaN(activityLevel) ||
isNaN(weightLossGoal) || weightLossGoal < 0) {
resultValueElement.textContent = "Invalid input";
resultValueElement.style.color = "red";
return;
}
var bmr = 0;
if (gender === "male") {
bmr = (10 * weight) + (6.25 * height) – (5 * age) + 5;
} else { // female
bmr = (10 * weight) + (6.25 * height) – (5 * age) – 161;
}
var tdee = bmr * activityLevel;
// Calculate daily calorie deficit needed (approx. 7700 kcal per kg of fat)
// To lose X kg/week, need X * 7700 / 7 kcal deficit per day
var dailyDeficit = weightLossGoal * (7700 / 7);
var targetCalories = tdee – dailyDeficit;
// Ensure target calories are not unrealistically low
if (targetCalories < 1200) { // General minimum for women, can be higher for men
targetCalories = 1200; // Setting a reasonable minimum
if (gender === "male" && targetCalories < 1500) targetCalories = 1500;
}
resultValueElement.textContent = Math.round(targetCalories) + " kcal";
resultValueElement.style.color = "#28a745"; // Success green
}