Fitness goal calculator
Mifflin-St Jeor gives your BMR, an activity factor turns it into TDEE, and the target intake follows at −20% for cutting, maintenance or +10% for bulking — with protein, fat and carbs broken down in grams plus an estimated weekly weight change.
Runs in your browserEvery computation happens in your browser — your data never leaves this device.
Body and goal
BMR uses the Mifflin-St Jeor equation; TDEE = BMR × activity factor (1.2 sedentary to 1.9 very active); protein scales with body weight, fat takes 25% of calories and carbs get the rest.
Result
1649 kcal/day2556 kcal/day112 g · 448 kcal71 g · 639 kcal367 g · 1469 kcal0.00 kg/weekWhat this tool does
- Starting a bulk or cut? Get maintenance and target calories first instead of adding or subtracting on a hunch.
- Meal prepping: copy the protein, fat and carb grams — weighing to grams beats estimating by “portions”.
- Training load changed? Switch the activity level from moderate to active and see how much TDEE moves.
- Stuck at a fat-loss plateau? Compare your actual weekly loss against the estimate to see whether you are off track.
Example
Input
Male, 30 years, 175 cm, 70 kg, moderate activity, goal “Maintain”
Output
BMR 1649 kcal/day; TDEE 2556 kcal/day; target intake 2556 kcal/day; protein 112 g (448 kcal), fat 71 g (639 kcal), carbs 367 g (1469 kcal); estimated weekly weight change 0.00 kg
BMR uses Mifflin-St Jeor: 10 × weight + 6.25 × height − 5 × age + 5 for men.
Frequently asked questions
What is the difference between BMR and TDEE?
BMR (basal metabolic rate) is what you would burn lying still all day, computed by Mifflin-St Jeor from weight, height, age and sex. TDEE multiplies that by an activity factor covering walking, training and chores — 1.2 sedentary up to 1.9 very active. Body weight tracks TDEE, not BMR.
Why −20% for cutting but only +10% for bulking?
Too large a deficit (say −40%) costs muscle, slows metabolism and wrecks training quality, so the usual advice is to start 15–25% below TDEE. Muscle gain needs only a small surplus: beyond +10–15% most of the extra goes to fat rather than muscle, hence the default +10%.
How are the macro targets derived?
Protein scales with body weight — 2.0 g/kg when cutting to protect muscle in a deficit, 1.6 g/kg for maintenance and 1.8 g/kg when bulking, all inside the 1.2–2.0 g/kg range bodies such as ACSM recommend for active people. Fat is fixed at 25% of target calories for hormones and fat-soluble vitamins, and carbs take whatever calories remain because they fuel training.
Why do I choose the activity factor myself?
The factor is an empirical multiplier that converts training volume into calories, and no formula can detect your actual routine. People tend to overestimate, so start with the more conservative option, track for two weeks and then move up or down a step based on the trend in your weight.
How reliable is the estimated weekly weight change?
It multiplies the daily calorie difference by 7 and divides by 7700 kcal/kg, which only describes the energy equivalent of fat. Real weight also moves with water, glycogen, gut contents and training-driven muscle gain, so swings of ±1 kg are normal — judge by the 2–4 week trend.
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