Quick answer: Daily calorie needs start from your basal metabolic rate, estimated by the Mifflin-St Jeor equation from weight, height, age and sex, then multiplied by an activity factor from 1.2 for sedentary up to 1.9 for very active. To lose about half a kilogram per week, eat roughly 500 calories below maintenance; to gain, add a similar surplus.
Last reviewed: September 2026
Key facts
- Uses the Mifflin-St Jeor formula — the most validated calorie formula.
- A daily deficit of 500 calories loses about 0.5 kg per week.
- Activity multiplies your resting burn by 1.2 to 1.9.
- Never eat below 1,200 (women) or 1,500 (men) calories without medical advice.
How many calories should you eat per day? It depends on your body size, age, activity and goal. This free calorie calculator uses the Mifflin-St Jeor formula to find your daily calorie target for losing, maintaining or gaining weight.
Enter your details and activity level. You get your resting burn, your total daily burn, and the calorie target that matches your goal.
How to use
- Enter your age, weight and height.
- Choose your activity level honestly.
- Pick your goal: lose, maintain or gain.
- Read your daily calorie target.
Calorie formula
Women: 10 × kg + 6.25 × cm − 5 × age − 161
Daily calories = result × activity ± 500
| Term | Meaning |
|---|---|
| BMR | Calories your body burns at complete rest. |
| TDEE | Total daily burn = BMR × activity level. |
| ±500 | Minus 500 to lose ~0.5 kg/week; plus 500 to gain it. |
Worked examples
Weight loss
Man, 30, 80 kg, 180 cm, moderate activity: BMR = 800 + 1,125 − 150 + 5 = 1,780. TDEE = 1,780 × 1.55 = 2,759. Weight-loss target = 2,259 calories/day.
Maintain weight
Woman, 30, 65 kg, 165 cm, light activity: BMR = 650 + 1,031 − 150 − 161 = 1,370. TDEE = 1,370 × 1.375 = 1,884 calories/day to maintain.
Activity multipliers
| Activity | Multiplier | Means |
|---|---|---|
| Sedentary | 1.2 | Desk job, little exercise |
| Light | 1.375 | Exercise 1-3 days a week |
| Moderate | 1.55 | Exercise 3-5 days a week |
| Very active | 1.725 | Hard exercise 6-7 days a week |
| Extra active | 1.9 | Physical job or twice-a-day training |
Frequently asked questions
How many calories should I eat to lose weight?
Eat about 500 calories below your total daily burn. That loses roughly 0.5 kg per week — the safe, sustainable rate. Faster loss usually comes back.
What is the Mifflin-St Jeor formula?
The most scientifically validated formula for resting calorie burn, published in 1990. It uses weight, height, age and sex. Most dietitians and apps use it as the base.
Why am I not losing weight on my calorie target?
Common causes: undercounting food (oils, drinks, snacks), overestimating activity, or water retention hiding fat loss. Track honestly for two weeks before adjusting.
Can I eat fewer than 1,200 calories?
Not without medical supervision. Very low intake risks muscle loss, nutrient deficiency and a slowed metabolism. Slow and steady beats extreme.
Do I need to exercise to lose weight?
No — diet drives weight loss. But exercise protects muscle, raises your calorie budget, and keeps the weight off. Combine both for best results.
Sources
- NHS — Guidance on calories and healthy weight
- CDC — Balancing food and activity for weight management
Key takeaways
- Your calorie target = body size × activity ± 500 for your goal.
- A 500-calorie daily deficit loses about 0.5 kg per week.
- Pick the activity level honestly — most people overestimate it.
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