Sedentary (Office job, little exercise)
Lightly Active (1-3 days/week)
Moderately Active (3-5 days/week)
Very Active (6-7 days/week)
Extra Active (Physical job + training)
Mild Weight Loss (250 kcal/day)
Standard Weight Loss (500 kcal/day)
Aggressive Weight Loss (750 kcal/day)
Maximum Safe Loss (1000 kcal/day)
To reach your goal, your daily intake should be:0Your Maintenance Calories (TDEE): 0
How to Calculate Your Calorie Deficit
A calorie deficit occurs when you consume fewer calories than your body burns to maintain its current weight. This fundamental principle of thermodynamics is the primary driver of weight loss. To calculate your target calories, we use the Mifflin-St Jeor Equation, which is widely considered the most accurate standard for estimating Basal Metabolic Rate (BMR).
The Science Behind the Math
First, we calculate your BMR, which is the energy your body requires at rest. Then, we apply an activity multiplier to determine your Total Daily Energy Expenditure (TDEE). Finally, we subtract your chosen deficit from the TDEE to find your weight loss target.
Real-Life Example:
A 35-year-old male, 180cm tall, weighing 90kg, who works an office job but exercises 3 times a week:
– BMR: ~1,880 calories
– TDEE (Active): ~2,585 calories
– 500 Calorie Deficit: 2,085 calories/day for weight loss.
Safe Weight Loss Guidelines
While it may be tempting to cut calories drastically, health experts generally recommend a deficit of 500 to 750 calories per day. This typically results in a sustainable weight loss of 0.5kg to 0.7kg (1 to 1.5 lbs) per week. Consuming fewer than 1,200 calories for women or 1,500 for men without medical supervision can lead to nutrient deficiencies and muscle loss.
function calculateDeficit() {
var gender = document.getElementById("gender").value;
var age = parseFloat(document.getElementById("age").value);
var weight = parseFloat(document.getElementById("weight").value);
var height = parseFloat(document.getElementById("height").value);
var activity = parseFloat(document.getElementById("activity").value);
var deficit = parseFloat(document.getElementById("deficit").value);
var resultDiv = document.getElementById("calc-result");
if (isNaN(age) || isNaN(weight) || isNaN(height)) {
alert("Please enter valid numbers for age, weight, and height.");
return;
}
var bmr;
if (gender === "male") {
bmr = (10 * weight) + (6.25 * height) – (5 * age) + 5;
} else {
bmr = (10 * weight) + (6.25 * height) – (5 * age) – 161;
}
var tdee = bmr * activity;
var target = tdee – deficit;
// Safety Floor
var floor = (gender === "male") ? 1500 : 1200;
var warning = "";
if (target < floor) {
warning = "Note: This is below the recommended minimum calorie floor (" + floor + " kcal). Consult a doctor.";
}
document.getElementById("target-calories").innerHTML = Math.round(target) + " kcal";
document.getElementById("tdee-val").innerText = Math.round(tdee) + " kcal";
resultDiv.style.display = "block";
if(warning !== "") {
document.getElementById("target-calories").innerHTML += warning;
}
}