How many calories should I eat to lose weight?

A daily deficit of 250–500 kcal produces safe, sustainable fat loss of 0.25–0.5 kg per week. Eating below your BMR (the minimum calories your body needs at rest) is not recommended without medical supervision.

Why does the calculator show multiple calorie targets?

Different people suit different rates of loss. The calculator shows targets for mild loss (−250 kcal), moderate loss (−500 kcal), and extreme loss (−1,000 kcal) so you can choose an approach that fits your lifestyle.

Does exercise change my calorie target?

Yes. Your activity level multiplier already accounts for your regular exercise. If you add extra workouts, you can increase your calorie intake proportionally to avoid too large a deficit.

Is my data sent to a server?

All calculations are pure JavaScript running in your browser. Our servers are not involved at any point.

Calorie calculator for weight loss

To lose weight, you need to eat fewer calories than your body burns. Enter your details to calculate your maintenance calories (TDEE), then see the calorie targets for mild, moderate, and fast weight loss, calculated using the Mifflin-St Jeor equation.

Biological sex

Age (years)

Height (cm)

Weight (kg)

Activity level

How it works

The Mifflin-St Jeor equation calculates basal metabolic rate (BMR), the calories your body needs at rest. Men: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5. Women: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161. The BMR is then multiplied by an activity factor (1.2–1.9) to produce your TDEE. Calorie targets are derived by adding or subtracting a daily deficit or surplus.

Processing runs in your browser

All calculations happen locally using pure JavaScript arithmetic. Our servers are not involved at any point.

Technical specification

The Mifflin-St Jeor equation was developed by Mifflin et al. and published in the American Journal of Clinical Nutrition 51:2 (1990). It is the most widely recommended BMR formula for adults. Activity multipliers follow the Harris-Benedict activity factor scale: Sedentary (×1.2), Lightly active (×1.375), Moderately active (×1.55), Active (×1.725), Very active (×1.9). A 500 kcal/day deficit corresponds to approximately 0.5 kg of fat loss per week (based on 3,500 kcal per pound of fat).

BMR formula: Mifflin-St Jeor (1990), AJCN 51:2
Activity multipliers: 1.2 (sedentary) to 1.9 (very active)
Weight loss target: TDEE − 500 kcal/day ≈ 0.5 kg/week loss
Browser API: Pure JavaScript arithmetic. No library

Related operations

To check a weight category for your height, try the BMI calculator. For body composition from circumference inputs, use the body fat calculator. To work out fat-free mass for protein targets, see the lean body mass calculator.

Frequently asked questions

How many calories should I eat to lose weight?: A daily deficit of 250–500 kcal produces safe, sustainable fat loss of 0.25–0.5 kg per week. Eating below your BMR (the minimum calories your body needs at rest) is not recommended without medical supervision.
Why does the calculator show multiple calorie targets?: Different people suit different rates of loss. The calculator shows targets for mild loss (−250 kcal), moderate loss (−500 kcal), and extreme loss (−1,000 kcal) so you can choose an approach that fits your lifestyle.
Does exercise change my calorie target?: Yes. Your activity level multiplier already accounts for your regular exercise. If you add extra workouts, you can increase your calorie intake proportionally to avoid too large a deficit.
Is my data sent to a server?: All calculations are pure JavaScript running in your browser. Our servers are not involved at any point.

Last reviewed May 26, 2026