How many calories should you eat?
Your calorie needs start with how much energy your body burns in a day, your maintenance calories. Eat that amount and your weight stays about the same. Eat less and you lose weight; eat more and you gain.
The calculator works this out in three steps:
- BMR (basal metabolic rate): the energy your body uses at complete rest, for breathing, circulation and keeping organs running.
- Maintenance calories (TDEE): BMR multiplied by an activity factor that covers daily movement and exercise.
- Your target: maintenance calories, minus a deficit for fat loss or plus a surplus for muscle gain.
How the calorie calculator works
We calculate BMR with the Mifflin-St Jeor equation, which research has found to be the most accurate simple equation for most adults.
BMR is then multiplied by your activity level, from 1.2 for a desk job with no exercise up to 1.9 for hard daily training plus a physical job. Want the full breakdown? The TDEE calculator shows where every calorie goes.
Choosing your pace
A kilogram of body fat stores roughly 7,700 kcal (about 3,500 kcal per pound). That is where the weekly estimates come from.
| Pace | Daily change | Approximate weekly change |
|---|---|---|
| Mild fat loss | −250 kcal | 0.25 kg (0.5 lb) |
| Moderate fat loss | −500 kcal | 0.45 kg (1 lb) |
| Fast fat loss | −750 kcal | 0.7 kg (1.5 lb) |
| Aggressive fat loss | −1,000 kcal | 0.9 kg (2 lb) |
| Lean bulk | +250 kcal | Slow, mostly lean gain |
| Standard bulk | +500 kcal | Faster gain, more fat |
Slower is usually better. In a study of elite athletes, a slower rate of weight loss preserved more lean mass and strength than a faster one. A useful rule is to lose no more than about 1% of your body weight a week.
Why your real number may differ
Every calorie calculator gives an estimate. Your true maintenance depends on things no equation can see: how much you move outside the gym, your muscle mass, genetics and how accurately you track food. Your body also adapts as you diet, burning a little less as you get lighter.
The practical fix is simple: eat at your target for 2–3 weeks and watch your weekly average weight.
- Losing faster than planned: add 100–200 kcal a day.
- Not losing: remove 100–200 kcal a day, or add more daily steps.
- Gaining too fast on a bulk: reduce your surplus.
Calories and body composition
Calories decide whether you gain or lose weight. What that weight is made of, muscle or fat, depends mostly on protein and training. Pair your calorie target with enough protein and regular resistance training, and more of the weight you lose will be fat. Read how to lower your body fat for the full approach.
Research behind this calculator
- Mifflin MD et al. (1990). A new predictive equation for resting energy expenditure in healthy individuals. American Journal of Clinical Nutrition.
- Frankenfield D et al. (2005). Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults. Journal of the American Dietetic Association.
- Hall KD et al. (2011). Quantification of the effect of energy imbalance on bodyweight. The Lancet.
- Garthe I et al. (2011). Effect of two different weight-loss rates on body composition and strength and power-related performance in elite athletes. International Journal of Sport Nutrition and Exercise Metabolism.
Last updated September 21, 2026.