Calorie Deficit Calculator to Lose Weight

Calorie Deficit Calculator

Sedentary (Little or no exercise) Lightly Active (Exercise 1-3 days/week) Moderately Active (Exercise 3-5 days/week) Very Active (Hard exercise 6-7 days/week) Extra Active (Very hard exercise/physical job)

Standard deficit for 0.5kg/week loss is 500 calories.

Your Personalized Results

Maintenance (TDEE)

–

kcal/day

Weight Loss Goal

–

kcal/day

Estimated Weekly Weight Loss: – kg

How to Use the Calorie Deficit Calculator

Achieving a weight loss goal requires a simple scientific principle: consuming fewer calories than your body burns. This calculator helps you determine your Total Daily Energy Expenditure (TDEE) and establishes a safe calorie target to reach your desired weight.

Understanding the Results

• BMR (Basal Metabolic Rate): The number of calories your body burns at rest just to keep your organs functioning.
• TDEE (Total Daily Energy Expenditure): The total calories you burn in a day including all physical activity and exercise.
• Calorie Deficit: The gap between what you burn and what you eat. A deficit of 3,500 calories roughly equals 0.45kg (1lb) of fat loss.

Safe Weight Loss Examples

Daily Deficit	Weekly Loss (Approx)	Intensity
250 kcal	0.25 kg / 0.5 lb	Easy/Sustainable
500 kcal	0.5 kg / 1.0 lb	Recommended
750 kcal	0.75 kg / 1.6 lb	Moderate
1000 kcal	1.0 kg / 2.2 lb	Aggressive

The Math Behind the Calculation

This calculator uses the Mifflin-St Jeor Equation, which is considered the most accurate formula for estimating BMR in healthy individuals:

For Men: (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) + 5
For Women: (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) – 161

Once your BMR is calculated, we multiply it by your activity multiplier (ranging from 1.2 to 1.9) to find your maintenance calories. Subtracting your goal deficit provides your final daily intake target.

function calculateCalories() { var gender = document.getElementById("gender").value; var weight = parseFloat(document.getElementById("weight").value); var height = parseFloat(document.getElementById("height").value); var age = parseFloat(document.getElementById("age").value); var activity = parseFloat(document.getElementById("activity").value); var deficitGoal = parseFloat(document.getElementById("deficitGoal").value); if (isNaN(weight) || isNaN(height) || isNaN(age) || isNaN(deficitGoal) || weight <= 0 || height <= 0 || age <= 0) { alert("Please enter valid positive numbers for weight, height, and age."); return; } // Mifflin-St Jeor Equation var bmr = 0; 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 Target var targetIntake = tdee – deficitGoal; // Health Floor Check (General guideline: 1200 women, 1500 men) var floor = (gender === "male") ? 1500 : 1200; var safeTarget = Math.max(targetIntake, floor); // Weekly Loss Estimation (7700 kcal per kg of fat approximately) var weeklyLoss = (deficitGoal * 7) / 7700; // Display Results document.getElementById("tdee-val").innerText = Math.round(tdee).toLocaleString(); document.getElementById("target-val").innerText = Math.round(safeTarget).toLocaleString(); document.getElementById("weekly-loss").innerText = weeklyLoss.toFixed(2); document.getElementById("results-area").style.display = "block"; // Scroll to results document.getElementById("results-area").scrollIntoView({ behavior: 'smooth', block: 'nearest' }); }