BMR Calculator — Your Resting Calorie Burn
Find out how many calories your body burns at complete rest. Compare the Mifflin-St Jeor, Harris-Benedict and Katch-McArdle equations — then add your activity level for the full daily picture (TDEE).
BMR Calculator
Required: biological sex is a term in every BMR equation (men carry more lean mass on average, so burn more at rest).
Range: 15–100 years
Range: 30–300 kg
Enter your height in centimeters (e.g., 170 cm)
Know your body fat? Add it to also get the lean-mass-based Katch-McArdle BMR — the most accurate for muscular bodies. Leave blank to use Mifflin-St Jeor and Harris-Benedict only.
Don't know your body fat %? Calculate it free*This calculator is for informational purposes only. Please consult a healthcare professional before making any health decisions. See our medical disclaimer for more information.
Quick Answer
What Is BMR (Basal Metabolic Rate)?
Your Basal Metabolic Rate is the number of calories your body burns at complete rest — the energy needed just to stay alive: breathing, circulation, organ function and temperature control. It’s typically 60–70% of your total daily calorie burn. This calculator estimates your BMR with the Mifflin-St Jeor equation (plus Harris-Benedict and, optionally, Katch-McArdle). Remember: BMR is your at-rest figure — to get the calories you actually use in a day, multiply it by an activity factor with the TDEE Calculator.
The BMR Formulas, Compared
This calculator runs the three most widely used equations so you can compare them side by side:
- Mifflin-St Jeor (1990) — the modern default and the most accurate for the general public.
BMR = 10·kg + 6.25·cm − 5·age + s(s = +5 for men, −161 for women). Shown as your primary result. - Harris-Benedict (revised 1984) — the original equation, still common. It usually lands a little higher than Mifflin-St Jeor.
- Katch-McArdle —
BMR = 370 + 21.6·lean mass (kg). Because it’s based on lean body mass it’s the most accurate for lean, muscular people — but it needs your body fat %. Add yours above to unlock it, or get a dedicated breakdown on the Katch-McArdle Calculator.
Which should you trust? For most people, go with Mifflin-St Jeor. If you’re lean and know your body fat %, Katch-McArdle is usually closest. The differences are small — all three are estimates within roughly 10% of a lab measurement.
BMR vs TDEE: Don’t Confuse the Two
This is the single most important thing to get right. BMR is what you burn at rest. TDEE is what you burn in a whole day, once you add movement, exercise and digestion. You never eat to your BMR — it’s simply the base you build on. To turn it into a usable daily number you multiply by an activity factor:
| Activity level | Multiplier | Who it fits |
|---|---|---|
| Sedentary | × 1.2 | Desk job, little exercise |
| Lightly active | × 1.375 | Light exercise 1–3 days/week |
| Moderately active | × 1.55 | Exercise 3–5 days/week |
| Very active | × 1.725 | Hard exercise 6–7 days/week |
| Extremely active | × 1.9 | Physical job or 2× daily training |
Rather than do that by hand, let the TDEE Calculator apply the multiplier for you — and if your goal is fat loss, the Weight Loss Calculator takes it one step further, subtracting a safe deficit to give you a daily calorie target.
How to Use This BMR Calculator
- Enter your stats. Gender, age, weight and height are all the Mifflin-St Jeor and Harris-Benedict equations need.
- Add body fat % (optional). Know it? Enter it to also get the lean-mass-based Katch-McArdle BMR. Estimate it first with the Body Fat % Calculator if needed.
- Read your BMR. Mifflin-St Jeor is your headline figure, with Harris-Benedict (and Katch-McArdle) shown for comparison.
- Add activity for the real number. Carry your stats to the TDEE Calculator to get the calories you actually burn — and eat to.
BMR Calculator — Limitations
- ⚠BMR equations are population estimates — they predict resting metabolism within about 10% for most people, but your true rate can differ.
- ⚠Mifflin-St Jeor and Harris-Benedict use only height, weight, age and sex, so they can’t see body composition. A muscular person’s BMR is under-stated; add body fat % for the Katch-McArdle estimate.
- ⚠These equations are validated for adults. For under-18s, who are still growing, treat the result as a rough guide only.
- ⚠BMR is not a calorie target. It does not include activity — never diet to your BMR.
- ⚠Pregnancy, thyroid conditions, medications and significant weight change all shift metabolic rate in ways a formula cannot capture.
Precision Tracking Tools
Monitor your baseline metrics with clinical accuracy to ensure you stay on target.
Custom Meal Design
Access foundational dietary blueprints structured for sustainable, long-term success.
Expert Coaching
Connect with certified professionals who can tailor strategies to your unique physiology.
Scientific References
- Mifflin MD, St Jeor ST, Hill LA, et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr. 1990;51(2):241–247. PubMed
- Roza AM, Shizgal HM. The Harris Benedict equation reevaluated: resting energy requirements and the body cell mass. Am J Clin Nutr. 1984;40(1):168–182. PubMed
- McArdle WD, Katch FI, Katch VL. Exercise Physiology: Nutrition, Energy, and Human Performance. 8th ed. Wolters Kluwer; 2015.
Related BMR Calculators
Have a more specific resting-metabolism question? These focused tools all run the same Mifflin-St Jeor engine as the calculator above:
Add this BMR Calculator to your site — free
Coaches, bloggers and gyms: embed this calculator on your page in one paste. Just keep the attribution link — that's how the tool stays free.
Explore More Tools
Each calculator feeds into the next — your data carries forward automatically through every step.
TDEE
Find out exactly how many calories your body burns daily — the foundation of every weight loss plan.
Katch-McArdle
Get the most accurate BMR and TDEE for lean, muscular bodies — calculated from your lean body mass and body fat %.
Weight Loss
How many calories to eat to lose weight — your maintenance, daily target, the deficit, and a realistic timeline to your goal.