TDEE Calculator

BMR vs RMR vs TDEE — what these numbers mean

Three terms you'll see in fitness writing, all related but distinct:

• BMR (Basal Metabolic Rate) — calories your body burns at complete rest, in a thermo-neutral environment, fasted. The energy needed to keep your organs functioning. Measured in lab settings; calculators estimate it.
• RMR (Resting Metabolic Rate) — slightly higher than BMR (typically 5–10%) because measurements aren't taken under such strict conditions. In practice, “BMR” and “RMR” are often used interchangeably.
• TDEE (Total Daily Energy Expenditure) — BMR plus activity. The actual calories you burn in a day, including walking, talking, eating (TEF), and exercise. This is the number you target for diet planning.

TDEE = BMR × activity multiplier. The activity multiplier accounts for everything you do beyond resting: NEAT (non-exercise activity thermogenesis — fidgeting, walking around), the thermic effect of food (TEF — calories burned digesting food, ~10% of intake), and structured exercise.

Three formulas — and which to use

Mifflin-St Jeor (1990) — the default

Most accurate general-purpose formula for adults. Uses age, sex, height, and weight. Validated across diverse populations. The American Dietetic Association recommends it as the default. Our calculator uses it unless you override.

Men: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5
Women: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161

Harris-Benedict (revised 1984)

The original 1919 version is outdated. The 1984 revision is similar to Mifflin-St Jeor in accuracy, but tends to overestimate slightly. Still widely cited.

Katch-McArdle

Uses lean body mass instead of total weight. The most accurate formula ifyou have an accurate body fat percentage measurement (DEXA scan, etc.) — but unreliable inputs make it worse than Mifflin-St Jeor. Recommended for athletes and anyone with substantial muscle mass who has a recent body composition test.

Activity multiplier — choose carefully

This is where most people overestimate. The multipliers:

• 1.2 — Sedentary: desk job, no exercise, mostly sitting. Most office workers default here.
• 1.375 — Lightly active: light exercise 1–3 days/week, or a job with some walking.
• 1.55 — Moderately active: moderate exercise 3–5 days/week (running, cycling, lifting).
• 1.725 — Very active: hard exercise 6–7 days/week.
• 1.9 — Extra active: physical job (construction, manual labor) PLUS daily training. Rare combination.

Most people self-rate one bracket too high. Be honest. If you're unsure between two, pick the lower one — you can always adjust upward after 2–3 weeks of tracking real-world results.

Cutting, maintenance, bulking — pick your goal

Cutting (fat loss): TDEE − 20%

A 20% deficit (about 400–600 calories below TDEE for most people) drives steady ~0.5–1 lb/week fat loss. Aggressive deficits (30%+) accelerate weight loss but tank energy, training quality, and adherence. They also drop more muscle along with fat. Slow and consistent wins for body composition.

Maintenance: TDEE

Eat at TDEE during recomposition phases (gaining muscle while losing fat — slow but possible for beginners and returning lifters), or as a planned diet break of 1–2 weeks every 8–12 weeks of cutting.

Bulking (muscle gain): TDEE + 10%

A modest 10% surplus (200–300 calories) supports muscle growth without excessive fat gain. Aim for ~0.5 lb/week. Faster bulks (1+ lb/week) deposit more fat per pound of muscle; for natural lifters past beginner stage, slow bulks have better composition outcomes.

Why your TDEE estimate may be off

Real-world TDEE varies ±10–15% from the formula prediction. Sources of error:

• Genetic variation in metabolism — some people genuinely run hotter or cooler.
• NEAT differences — fidgeters can burn 500+ extra calories per day vs. still people. Hard to predict.
• Adaptive thermogenesis — your metabolism slows in a sustained deficit (10–20% drop) and speeds up in a surplus.
• Calorie tracking errors — most people underreport intake by 20–40% on average. Food labels themselves have ±20% legal tolerance.

The fix: track actual results for 2–3 weeks at the calculator's recommended intake. If your weight isn't moving as expected, adjust by 100–200 calories and re-check after another 2 weeks. Treat the calculator output as a starting hypothesis, not a fixed truth.

Macros — protein matters most

For body composition, protein is the most important macronutrient to track. Aim for 0.7–1.0 g per pound of body weight (1.6–2.2 g/kg) — higher in a cut to preserve muscle, lower in a bulk where total calories are doing the work.

Fill remaining calories with a balance of carbs and fats according to preference, sport, and what helps adherence. Use our Macro Calculator to set targets. For weight tracking, the BMI Calculatorcan show whether you're moving toward or away from a target range, though body composition (mirror, photos, waist measurement) is a better indicator than scale alone.