BMR & TDEE Calculator
Calculate your basal metabolic rate and total daily calorie burn from height, weight, age, and activity level — with cutting and bulking targets.
How to use this calculator
- 1Enter your sex, age, height, and weight.
- 2Choose the activity level that matches a typical week — most people overestimate this.
- 3If you know your body fat percentage, add it to switch to the more accurate Katch-McArdle equation.
- 4Use the maintenance figure as a starting point and adjust after two to three weeks of real data.
How it works
BMR and TDEE equations
Mifflin-St Jeor (men): BMR = 10w + 6.25h − 5a + 5 Mifflin-St Jeor (women): BMR = 10w + 6.25h − 5a − 161 Katch-McArdle: BMR = 370 + 21.6 × lean mass (kg) TDEE = BMR × activity multiplier w = kg, h = cm, a = years
Basal metabolic rate is what your body burns at complete rest just staying alive — breathing, circulating blood, maintaining temperature, running the brain. It typically accounts for 60–70% of total daily burn. Multiplying by an activity factor adds everything else: exercise, movement, and the energy spent digesting food. Katch-McArdle is the most accurate equation when you know your body fat, because muscle burns more at rest than fat does and the other equations only see total weight.
Worked example
A 32-year-old man, 70 inches and 180 lb: converted to 177.8 cm and 81.6 kg, Mifflin-St Jeor gives 10(81.6) + 6.25(177.8) − 5(32) + 5 = 1,772 kcal. At a moderate activity multiplier of 1.55, his maintenance is about 2,746 kcal a day.
BMR & TDEE Calculator: the complete guide
BMR, RMR, and TDEE
Basal metabolic rate is measured under strict conditions: complete rest, no food for twelve hours, a thermally neutral room, immediately after waking. Resting metabolic rate is the same idea measured less strictly, and comes out 5–10% higher. In practice the terms are used interchangeably, and the equations above predict something between the two.
Total daily energy expenditure is everything: BMR plus the energy cost of digestion (about 10% of intake), plus deliberate exercise, plus non-exercise activity — fidgeting, walking to the car, standing. That last component varies enormously between people and is the main reason two people of identical size can have TDEEs several hundred calories apart.
Choosing the right activity multiplier
This is where most estimates go wrong, and the error is nearly always in the same direction. The multipliers describe a whole week, not your best day. Three gym sessions on top of a desk job is "light to moderate", not "active" — a 1.375 to 1.55, not 1.725.
"Very active" at 1.9 means manual labour or twice-daily training, not an enthusiastic hour at the gym. If you have a desk job, your baseline is sedentary and exercise moves you up from there. When in doubt, pick the lower option: it is easier to add calories after two weeks of unwanted weight loss than to explain away a stalled cut.
Using the number to lose or gain weight
A pound of body fat stores roughly 3,500 calories, so a 500-calorie daily deficit predicts about a pound of loss per week. That prediction holds well for the first several weeks and then slows, because a lighter body burns less and the body compensates with reduced spontaneous movement.
For gaining, a surplus of 250–500 calories a day supports muscle growth without excessive fat gain. Beyond that, the extra is mostly stored as fat — muscle can only be built so fast regardless of intake.
Never eat below your BMR for extended periods. It rarely accelerates fat loss and reliably costs lean mass, energy, and adherence.
Why the number is only a starting point
The equations were fitted on populations, and individual metabolic rates scatter around the prediction by 10–15% in each direction. Thyroid function, genetics, past dieting history, sleep, and body composition all shift the real value.
The reliable approach is to treat the estimate as hypothesis one. Eat at the predicted maintenance for two to three weeks, weigh yourself consistently, and take the trend line — not any single day. If weight is stable, the estimate was right. If it moved, adjust by 100–200 calories and repeat. Two weeks of your own data beats any equation.
Frequently asked questions
Which BMR equation is most accurate?
Mifflin-St Jeor is the most accurate for the general population and is what most current guidance recommends. If you know your body fat percentage, Katch-McArdle is better still, because it works from lean mass — the tissue that actually drives resting metabolism.
Should I eat back the calories I burn exercising?
No, not if you used an activity multiplier. The multiplier already includes your exercise, so logging workouts separately and eating those calories back counts them twice. Only eat back exercise calories if you set the activity level to sedentary and track every session individually.
Why has my weight loss stalled at the same calories?
A lighter body has a lower TDEE, so the deficit that worked at the start shrinks as you lose. Adaptive thermogenesis adds to this — the body reduces spontaneous movement and slightly lowers resting burn. Recalculate every 10–15 pounds, and expect to adjust downward or add activity.
Does eating more often speed up metabolism?
No. The thermic effect of food is roughly 10% of total intake regardless of how it is divided across the day. Six small meals and two large ones with the same total produce the same energy expenditure. Meal frequency is worth choosing for appetite control and convenience, not metabolism.