Free tool · Reviewed July 25, 2026
TDEE & BMR calculator
What you burn at rest, what you burn in a day — and the part most calculators leave out: both numbers shrink as you do.
Key takeaways
- BMR is what you burn at complete rest; TDEE is BMR multiplied by an activity factor — the total you actually burn in a day.
- This calculator uses Mifflin-St Jeor, the equation clinical nutrition defaults to because it validates better than Harris-Benedict on modern populations.
- Any of these equations is an estimate with roughly 10% individual error either way — treat the range as the answer, not the single number.
- TDEE falls as you lose weight: a smaller body costs less to run, which is the mechanical reason a deficit that worked at the start stops working later.
- On a GLP-1 that matters twice over — appetite drops at the same time TDEE does, so the gap between what you eat and what you burn narrows from both ends.
Mifflin-St Jeor is an estimate, not a measurement — individual results vary by roughly 10% either way even in validation studies, which is why the range above matters more than the single figure.
Nothing you enter is stored or sent anywhere. General information, not medical or nutritional advice.
The moving target nobody warns you about
Every calorie target has an expiry date. Lose 20 pounds and you are running a smaller body: less tissue to maintain, less mass to move. TDEE falls with it, so the deficit that drove steady loss in month one is a smaller deficit by month four — with nothing about your eating having changed.
On a GLP-1 this compounds. Appetite suppression is usually strongest early and often eases as the body settles at a stable dose, so intake tends to creep up at the same time expenditure drifts down. People read that as the medication failing. It is arithmetic. The practical fixes are recalculating here every 10–15 pounds, tracking waist rather than only weight, and protecting protein intake so the weight you lose is fat rather than muscle.
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Common questions about TDEE and BMR
What is the difference between BMR and TDEE?
BMR (basal metabolic rate) is the energy your body uses at complete rest just to stay alive — breathing, circulation, temperature, organ function. TDEE (total daily energy expenditure) is that figure multiplied by an activity factor to account for movement, exercise and digestion. TDEE is always the larger number, and it is the one relevant to eating for weight change.
How accurate are TDEE calculators?
They are estimates, not measurements. Mifflin-St Jeor is the best-validated of the common equations, and even it carries roughly a 10% error band for an individual — meaning a calculated 2,000 kcal could genuinely be 1,800 or 2,200 for you. Body composition is the main reason: two people at identical height, weight, age and sex burn different amounts if one carries more muscle. Use the number as a starting point and adjust based on what actually happens over several weeks.
Does TDEE change as you lose weight?
Yes, and this is the part that catches people out. A lighter body costs less energy to move and maintain, so TDEE falls as weight comes off. A deficit that produced steady loss at the start becomes a smaller deficit — or none at all — at a lower weight, without anything about your behaviour changing. Recalculating every 10 to 15 pounds keeps the target honest.
Why does my weight loss stall on a GLP-1 even though I am eating less?
Usually because both sides of the equation moved. TDEE dropped with your weight, while the appetite suppression that made eating less effortless at the start often eases as your body adapts to a stable dose. Neither means the drug stopped working. Recalculating TDEE at your current weight, tracking waist rather than only weight, and protecting protein intake address the three most common causes of a plateau.
Which activity level should I choose?
Most people overestimate. "Sedentary" fits desk work with no structured exercise, and it fits more people than they expect — deliberate gym sessions three to five times a week are what "moderately active" describes, not a busy day. If you are unsure, pick the lower option: it is easier to notice you are losing faster than expected and eat more than to spend months wondering why an inflated target is not working.
Uses the Mifflin-St Jeor equation. Estimates only — individual expenditure varies by roughly 10% either way, and more if body composition is unusual. General information, not medical or nutritional advice.