How the calculator works
Your total daily energy expenditure (TDEE) is estimated in two steps. First, your basal metabolic rate — the calories your body burns at complete rest — is calculated with the Mifflin-St Jeor equation (1990), the formula the Academy of Nutrition and Dietetics recommends. If you enter a body-fat percentage, the Katch-McArdle equation is used instead, since it works from lean body mass. (Both are shown in full on the BMR calculator page.) Second, that resting number is multiplied by an activity factor:
| Activity level | Multiplier |
|---|---|
| Sedentary (desk job, little exercise) | 1.2 |
| Light (1–3 workouts/week) | 1.375 |
| Moderate (3–5 workouts/week) | 1.55 |
| Very active (6–7 workouts/week) | 1.725 |
| Athlete / physical job | 1.9 |
The result — maintenance calories — is the intake at which your weight holds steady. Every fat-loss or muscle-gain target is just this number moved down or up.
Choosing your activity level honestly
This input causes more error than any other, and the error almost always runs one direction: people overestimate. Three gym sessions a week feels like a lot, but if the other 165 hours are spent at a desk and on a sofa, "Light" describes your week better than "Moderate". The multipliers describe your whole life, not your best days — a nurse who never trains can out-burn an office worker with a perfect gym record.
Two honest rules: count only the workouts you actually do (not the ones you plan to do), and when torn between two levels, pick the lower one. Underestimating costs you nothing — you simply lose slightly faster or gain slightly slower than predicted. Overestimating puts your "deficit" at maintenance, and that's the classic story behind "I'm eating 1,800 and not losing".
Maintenance first: confirm before you cut
Any formula is a prediction — good to roughly ±10%, which on 2,500 kcal is a 250-kcal spread. So before building a diet on the estimate, verify it: eat your calculated maintenance for two weeks, weigh yourself daily, and compare the weekly averages. Weight steady? The number is right. Drifting up or down by more than ~0.25 kg a week? Shift your target by 100–200 kcal and re-check. Two weeks of tracking beats any equation, because it measures your metabolism, not the population average.
Adjusting for your goal
Once maintenance is confirmed, the adjustments are modest. For fat loss, a 20% reduction (roughly 500 kcal for most people) produces steady progress you can actually sustain — the calorie deficit calculator lets you pick your deficit size and see the projected weekly loss. For muscle gain, a 10% surplus (about 250 kcal) is plenty; bigger surpluses mostly add fat — the muscle gain calculator covers realistic rates by training experience.
Then comes the part no calculator does for you: hitting the target daily. That's where most plans die — not in the math, but in the logging. The CoachRight client app makes it fast: snap a nutrition label and the AI reads the macros for you, and your coach sees your food diary live instead of asking "how did the week go?". If you're a trainer setting calorie targets for clients, start a free 14-day trial and manage targets, programs and check-ins in one place.