TDEE & BMR
calculator
Three BMR formulas side-by-side. Calorie targets for cutting and bulking. Imperial or metric. With the activity-multiplier honesty most calculators skip.
How the math works
BMR (Basal Metabolic Rate) is the calories your body burns at rest. TDEE (Total Daily Energy Expenditure) is BMR multiplied by an activity multiplier to account for movement, exercise, and the thermic effect of food.
The three formulas above use different inputs to estimate BMR:
BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5
Mifflin-St Jeor (female)
BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161
Harris-Benedict (revised, male)
BMR = 88.362 + 13.397 × weight + 4.799 × height − 5.677 × age
Katch-McArdle (uses lean body mass)
BMR = 370 + 21.6 × LBM(kg)
where LBM = weight × (1 − bodyfat%/100)
TDEE is then BMR × an activity multiplier from 1.2 (sedentary) to 1.9 (extra active).
Worked example
A 30-year-old, 5'10" (178 cm), 180 lb (82 kg) male at moderate activity.
- Mifflin-St Jeor BMR: 10×82 + 6.25×178 − 5×30 + 5 = 1,788 kcal
- TDEE at 1.55× (moderate): 2,771 kcal
- Cut target (−500 kcal): 2,271 kcal — roughly 1 lb (0.45 kg) loss per week
- Bulk target (+250 kcal): 3,021 kcal — roughly 0.5 lb (0.23 kg) gain per week
When this calculator is wrong
The activity multiplier you pick is the single biggest source of error in this estimate. Doubly-labelled water studies (Westerterp 2017) have shown that "moderately active" typically overestimates real-world TDEE by 5–15% for people with desk jobs, because the formula doesn't distinguish 4 hours of training per week from 4 hours of training embedded in an otherwise sedentary lifestyle. The exception is truly high-volume athletes, for whom the upper tiers can actually underestimate.
- It assumes "average" body composition. Mifflin-St Jeor underestimates BMR by 5–10% for highly muscular individuals (above ~15% LBM-to-total ratio compared to population norms). This is the case where Katch-McArdle wins — but only if your body fat % is measured reliably (DEXA, BodPod, calipers, not a bathroom scale).
- Population validity matters. Mifflin-St Jeor was validated on healthy adults aged 19–78. It's less accurate at the extremes — very low BMI, very high BMI, elderly, athletes in peak training.
- It treats the 3,500-kcal-per-pound rule as linear. Hall et al. (2011) showed that long-term weight loss is non-linear; expect about 1 lb/week for the first 4–8 weeks of a 500 kcal/day deficit, then progressively less as the body adapts.
- It can't see your NEAT. Non-Exercise Activity Thermogenesis (fidgeting, walking, standing) varies by 300–400 kcal/day between individuals and is the biggest single source of unexplained metabolic variance.
What to do with the result
Use the TDEE number as a starting point, not a target. Track your actual intake and weight for two weeks. If your weight hasn't changed at the calculated maintenance number, that's your maintenance. If it has, adjust by 100–200 kcal/week until it stabilises.
For a cut: most evidence supports a 20–25% deficit (so ~500 kcal for the reference subject above) with protein at 1.0 g/lb of bodyweight or higher (Helms et al. 2014) to preserve lean mass. For a bulk: 250–500 kcal surplus is typically enough; larger surpluses add fat without adding muscle past a point.
Common questions
- What's the difference between BMR and TDEE?
- BMR is the calories you'd burn if you stayed in bed all day — just keeping your organs running. TDEE is BMR plus the calories you burn moving, exercising, and digesting food. TDEE is the more useful number for setting calorie targets.
- Which BMR formula is most accurate?
- For most people, Mifflin-St Jeor (1990). It was the formula recommended by the American Dietetic Association after a systematic comparison of the available equations. Katch-McArdle is more accurate if you know your body fat percentage reliably — for highly lean or muscular individuals it's the better call. Harris-Benedict (revised 1984) is fine but slightly less accurate than Mifflin on average.
- How accurate is the TDEE calculator?
- The BMR portion is typically within 10% of measured values (indirect calorimetry) for healthy adults. The activity-multiplier portion has much larger error — easily 10–20% — because the multipliers are coarse and self-reported activity is unreliable. The combined estimate is a useful starting point that needs real-world calibration over 2 weeks.
- How many calories should I eat to lose 1 lb per week?
- The classic rule is a 500 kcal/day deficit (3,500 kcal/week, the energy content of 1 lb of fat). This works well for the first 4–8 weeks. After that, the body adapts and real-world loss slows — expect to need slightly larger deficits or longer timelines for sustained loss.
- Should I subtract exercise calories from my intake?
- No, if you're using TDEE-based targets. Your TDEE already includes your exercise via the activity multiplier. Subtracting exercise on top of that would double-count. The exception is if you set your target using BMR × 1.2 (sedentary) and add exercise calories manually — but that's a less reliable approach.