Free calculator
Calorie calculator
Work out your basal metabolic rate (BMR) and total daily energy expenditure (TDEE) with the Mifflin-St Jeor formula, the current standard. You'll also see how many calories you need for whatever rate of weight change you're aiming at.
Your details
Your daily expenditure
Maintenance calories (TDEE)
2,633kcal
What you burn on an average day. Eat this and your weight holds steady.
Calories for your goal
A kilo of body fat is roughly 7,700 kcal. That's where these targets come from: the weekly rate you pick is spread across the seven days.
| Goal | Daily calories | Adjustment |
|---|
Which rate to choose: losing between 0.5 % and 1 % of your bodyweight per week is the range that best preserves muscle mass. For gaining, 0.25 to 0.5 kg per week; faster than that almost always means more fat, not more muscle.
What BMR and TDEE are
Your BMR (basal metabolic rate) is the energy your body burns at complete rest: breathing, pumping blood, holding temperature, repairing tissue. It accounts for 60-70 % of everything you burn in a day.
Your TDEE (total daily energy expenditure) is your BMR plus everything else: training, steps, work, digestion and involuntary movement. It's the figure that actually matters for planning your food, and you get it by multiplying BMR by an activity factor.
The formula: Mifflin-St Jeor
This is the equation used by both this calculator and the Forge app. Published in 1990, it replaced Harris-Benedict as the standard because it's more accurate in modern populations:
BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) + S
Where S is +5 for men and −161 for women. Then: TDEE = BMR × activity factor, using the factors 1.2 · 1.375 · 1.55 · 1.725 · 1.9 depending on the level you pick above.
About the activity factor
This is the least exact part of the calculation, and where most people get it wrong: almost everyone overestimates. The factor should reflect your whole week, including your job and the days you don't train. If you have a desk job and train four times a week, you're "moderate" (1.55), not "high".
Limitations
- It's a starting estimate. The typical error of these formulas is around ±10 %. On 2,500 kcal, that's a 250 kcal margin.
- It ignores body composition. Two people at the same weight and height but with different muscle mass burn different amounts, and the formula gives them the same number.
- Metabolism adapts. In a prolonged deficit your expenditure drops: you move less without noticing and your body becomes more efficient.
That's why the right number isn't the one a formula gives you — it's the one the scale confirms. Use this figure as a starting point, hold it for two or three weeks while logging what you eat, and adjust based on how your weight actually moves.
Frequently asked questions
How many calories should I eat to lose weight?
A sensible deficit is 10-20 % below maintenance, which for most people is 300 to 500 kcal a day. Bigger deficits speed things up short term, but they're much harder to sustain and increase muscle loss.
Should I eat back the calories I burn training?
No, not if you picked your activity factor properly: training is already included in your TDEE. Adding the calories your watch or cardio app estimates on top means counting them twice, and those estimates tend to be generous.
Does BMR drop as I lose weight?
Yes. A lighter body needs less energy to run, and there's some metabolic adaptation on top. It's normal to recalculate your calories every 4-6 weeks or every 3-4 kg lost.
Mifflin-St Jeor or Harris-Benedict?
Mifflin-St Jeor. The Harris-Benedict revision tends to overestimate expenditure by around 5 % in modern populations, and nutrition guidelines have recommended Mifflin as the reference predictive equation for years.
From a number to a plan
Forge works out your calories, splits them into macros, adjusts the target on its own based on how your real weight moves, and lets you log meals and workouts in the same app.
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These calculators provide estimates for informational purposes and do not replace the judgement of a qualified training or health professional.