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BMR Calculator — Calculate Your Basal Metabolic Rate

BMR is the number of calories your body burns at complete rest to keep basic functions running. It's your energy baseline — but not your full calorie needs.

Calculate Your BMRMifflin-St Jeor
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BMR vs TDEE — what you should use

BMR measures your resting energy expenditure — your body in complete inactivity. It is a theoretical baseline value, not a calorie target.

**TDEE is the number you should actually use.** Whether you want to lose weight, maintain, or build muscle — all calorie target decisions should be based on TDEE, not BMR.

Why you can't use BMR as a calorie target
You burn more than BMR even at rest
NEAT (non-exercise activity — standing, walking, fidgeting) adds 15–50% on top of BMR for most people. Your body is never in complete BMR rest during a normal day.
Thermic effect of food (TEF)
Digestion consumes 8–15% of your calorie intake. Protein has a TEF of 25–30%. This is not included in BMR.
Exercise is added on top
A 60-minute training session can burn 300–600 kcal — all on top of BMR. The only way to include this is through the TDEE multiplier.
Calculate your TDEE instead

How BMR is calculated — the formulas

CalculEat uses **Mifflin-St Jeor (1990)** as the primary formula — the most validated for the general population with normal to moderately elevated body fat.

FormulaStrengthBest for
Mifflin-St Jeor (1990)Most validated generallyGeneral population, ±10%
Harris-Benedict (revised)Long history, wide useGeneral population
CunninghamRequires body fat % (LBM-based)Athletes, low body fat
Oxford/HenryWHO-recommended, age-adjustedOlder adults, children

No formula is exact. All formulas give a population-based estimate — calibrating against actual weight trends is the only method that gives an individually accurate result.

Frequently Asked Questions

What is the difference between BMR and TDEE?
BMR (Basal Metabolic Rate) is the calories your body burns at complete rest — without movement, digestion or activity. TDEE (Total Daily Energy Expenditure) is your actual total calorie needs per day, including all activity. TDEE = BMR × activity multiplier. TDEE is the number to use when planning calories.
Is BMR the same as calorie needs?
No. BMR is just the baseline — your resting burn rate. Most adults have a TDEE that is 20–80% higher than BMR depending on activity level. Eating at BMR without accounting for activity creates a severe deficit in practice, which can lead to muscle loss and metabolic downregulation.
Is it dangerous to eat below your BMR?
Consistently eating below your BMR is not recommended for most people. It risks triggering adaptive thermogenesis (the body lowers metabolism), increasing muscle loss and causing nutritional deficiencies. Under medical supervision it may be justified in certain cases, but generally calorie goals should be set below TDEE — not below BMR.
How does BMR change with age?
BMR typically drops 1–2% per decade after age 20. This is primarily due to decreased muscle mass (sarcopenia) rather than age itself. Strength training and adequate protein intake can significantly slow this decline. That's why TDEE decreases with age in inactive people but can remain stable in those who train.
Which BMR formula is most accurate?
Mifflin-St Jeor (1990) is considered the most accurate formula for the general population with normal body fat, with an average deviation of about ±10%. For people with unusual body composition (very low or high body fat), formulas like Cunningham (based on LBM) give better precision. The only formula that gives a calibrated result is tracking actual weight trend against calorie intake over 2–3 weeks.

Go from BMR to a real calorie goal

BMR is the foundation. TDEE is the number you actually use — and CalculEat helps you log against it.

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