Calculate your daily calorie intake for sustainable weight loss.
Male
Female
Sedentary (Little/no exercise)
Lightly Active (1-3 days/week)
Moderately Active (3-5 days/week)
Very Active (6-7 days/week)
Extra Active (Hard labor/training)
Mild Weight Loss (0.25 kg / week)
Standard Weight Loss (0.5 kg / week)
Extreme Weight Loss (0.75 kg / week)
Maximum Weight Loss (1.0 kg / week)
Your Daily Targets
Maintenance (TDEE)
0
kcal/day
Deficit Goal
0
kcal/day
*Calculated using the Mifflin-St Jeor Equation, the most accurate standard formula for metabolic rate.
How to Use a Calorie Deficit to Lose Weight
A calorie deficit occurs when you consume fewer calories than your body burns in a day. This state forces your body to use stored energy (body fat) for fuel, resulting in weight loss. To lose weight safely and effectively, understanding your numbers is the first step.
The Math of Weight Loss
Scientific research generally suggests that a deficit of 3,500 calories leads to approximately 0.45 kg (1 lb) of fat loss. By maintaining a daily deficit of 500 calories, you can aim to lose about 0.5 kg per week, which is considered a sustainable and healthy rate of weight loss by medical professionals.
Calculation Factors Explained
BMR (Basal Metabolic Rate): The energy your body needs to perform basic life-sustaining functions (breathing, circulation) at rest.
TDEE (Total Daily Energy Expenditure): Your BMR plus the energy used for physical activity. This is your "maintenance" level.
Activity Level: This accounts for your lifestyle, from desk jobs to professional athletic training.
Safety Guidelines
It is generally recommended that men do not drop below 1,500 calories per day and women do not drop below 1,200 calories per day without medical supervision. Rapid weight loss can lead to muscle loss, nutrient deficiencies, and metabolic slowdown.
function calculateCalorieDeficit() {
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 activity = parseFloat(document.getElementById('activity').value);
var deficitAmount = parseFloat(document.getElementById('goal').value);
var errorColor = "#ffeded";
var normalColor = "#ccc";
// Reset borders
document.getElementById('weight').style.borderColor = normalColor;
document.getElementById('height').style.borderColor = normalColor;
document.getElementById('age').style.borderColor = normalColor;
// Validation
if (!weight || weight <= 0) {
document.getElementById('weight').style.borderColor = "red";
alert("Please enter a valid weight.");
return;
}
if (!height || height <= 0) {
document.getElementById('height').style.borderColor = "red";
alert("Please enter a valid height.");
return;
}
if (!age || age <= 0) {
document.getElementById('age').style.borderColor = "red";
alert("Please enter a valid age.");
return;
}
// Mifflin-St Jeor Equation
var bmr;
if (gender === "male") {
bmr = (10 * weight) + (6.25 * height) – (5 * age) + 5;
} else {
bmr = (10 * weight) + (6.25 * height) – (5 * age) – 161;
}
// TDEE Calculation
var tdee = bmr * activity;
// Deficit Goal
var finalDeficit = tdee – deficitAmount;
// Safety Floor check
var minimumCalories = (gender === "male") ? 1500 : 1200;
var displayCalories = finalDeficit;
if (finalDeficit < minimumCalories) {
displayCalories = minimumCalories;
}
// Update UI
document.getElementById('tdee-val').innerHTML = Math.round(tdee).toLocaleString();
document.getElementById('deficit-val').innerHTML = Math.round(displayCalories).toLocaleString();
document.getElementById('calorie-results').style.display = "block";
// Scroll to results
document.getElementById('calorie-results').scrollIntoView({ behavior: 'smooth', block: 'nearest' });
}