BMR is the energy your body spends at complete rest — the cost of keeping your heart, lungs, brain and cells running while you lie still. TDEE is BMR plus everything else: digesting food, training, and every step you take. BMR is a component; TDEE is the total. A calorie calculator estimates the first with an equation and turns it into the second with a multiplier.
What BMR is
BMR stands for basal metabolic rate. Measured properly it means the energy used by someone lying awake, fasted for 12 hours, in a comfortable room, doing nothing. For most adults it is the single largest part of the day's energy use — 45–70% of the total depending on age and how active the rest of the day is.
Because almost nobody has it measured, calculators estimate it. Ours uses the Mifflin-St Jeor equation, which needs four things — sex, weight, height and age:
| Sex | Equation |
|---|---|
| Men | 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5 |
| Women | 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161 |
For a 30-year-old woman, 165 cm and 65 kg: 650 + 1,031.25 − 150 − 161 = 1,370 kcal. That is what her body would spend if she spent the day in bed, and it is not a number anyone is meant to eat at.
What TDEE adds on top
Three things sit on top of BMR:
- TEF — the thermic effect of food, the energy spent digesting and storing a meal. Roughly a tenth of intake.
- EAT — exercise activity thermogenesis, the training sessions themselves.
- NEAT — non-exercise activity thermogenesis, everything else you do on your feet.
A calculator does not estimate these separately. It folds all three into one multiplier and applies it to BMR. That is a simplification, but it is the same simplification every calorie calculator makes; the differences between them are in the equation and the multiplier values (see why TDEE calculators disagree).
The multiplier table we use
Most calculators ask a single "activity level" question. Ours builds the multiplier from two answers — training sessions per week, and how much you move outside training — because a desk worker who lifts five times a week and a warehouse worker who lifts five times a week are not the same person.
| Sessions per week | Base | + NEAT sedentary (−0.05) | + NEAT moderate (0) | + NEAT very active (+0.10) |
|---|---|---|---|---|
| 0 | 1.2 | 1.15 | 1.20 | 1.30 |
| 1–3 | 1.375 | 1.325 | 1.375 | 1.475 |
| 4–6 | 1.55 | 1.50 | 1.55 | 1.65 |
| 7+ | 1.725 | 1.675 | 1.725 | 1.825 |
TDEE = round(BMR × (base + NEAT adjustment))
Apply it to the 65 kg woman above, BMR 1,370:
| Profile | Multiplier | TDEE |
|---|---|---|
| No training, sedentary job | 1.15 | 1,576 kcal |
| 1–3 sessions, moderate NEAT | 1.375 | 1,884 kcal |
| 4–6 sessions, very active outside the gym | 1.65 | 2,261 kcal |
| 7+ sessions, very active | 1.825 | 2,500 kcal |
Same body, same BMR, a 924 kcal spread. The BMR line is fixed by who you are; the TDEE line is mostly decided by what you do.
In plain terms: BMR is the engine idling; TDEE is the fuel used on the actual journey.
Which number you actually eat at
Targets come from TDEE, always. Our calculator's three branches are:
- Maintain —
target = TDEE - Lose —
target = TDEE − daily deficit, where the deficit comes from a weekly rate of body weight and is capped at 35% of TDEE, with a calorie floor applied afterwards - Gain —
target = TDEE + daily surplus, same rate logic
BMR never appears in a target directly. If someone with a TDEE of 1,884 set their intake at their BMR of 1,370, they would be running a 514 kcal daily deficit — more than a quarter of their expenditure — without having chosen to. This is why the two numbers are worth keeping apart in your head, and why our calorie calculator shows BMR as an intermediate step and builds every target from the TDEE line.
This is arithmetic, not medical advice. The multipliers are the app's defaults for turning an equation into a day; your own logged intake and weight trend are the real test of the result.
The short version
BMR is what you spend at rest; TDEE is what you spend in a real day. Our calculator estimates BMR with Mifflin-St Jeor and multiplies it by 1.15–1.825 depending on training sessions and everyday movement. Every calorie target starts from the TDEE line — eating at BMR is a large, accidental deficit, not maintenance. Educational overview only — not medical advice.