Free tool
BMR calculator
A free BMR calculator using the Mifflin–St Jeor equation, with the formula shown, an optional activity multiplier, and a clear line between resting energy and a target.
Enter your height, weight, age, and the sex the equation should use. Nothing you type here leaves your browser.
An estimate of energy used at rest, not a daily calorie target. Nothing you enter is sent anywhere or stored.
The equation
Mifflin–St Jeor, published in 1990
Still the equation most commonly recommended for healthy adults. The two versions differ by exactly 166 kcal. That is the whole of what the sex variable does here. It selects a constant fitted to a reference group.
Male
10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5
80 kg, 180 cm, 30 years → 800 + 1125 − 150 + 5 = 1,780 kcal
Female
10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161
If your body composition sits closer to the other reference group, the other constant will predict you better.
The distinction
BMR, RMR, and what people actually mean
Basal metabolic rate is measured after an overnight fast, at rest, in a thermoneutral room. Resting metabolic rate is the same idea under less strict conditions and runs a few percent higher. Almost every BMR calculator on the internet, this one included, is estimating RMR.
Read it right
Resting energy is not a calorie target
Your resting estimate is what you would burn lying still all day. Nobody does that, and eating to it is eating well below what you spend.
The multiplier
Physical activity bands
What you actually burn is resting energy plus movement, training, and the cost of digesting food. These bands come from the Institute of Medicine's Dietary Reference Intakes, and the calculator shows which value inside the band it used. That multiplier moves the final figure more than the equation underneath it does.
| Band | PAL | Roughly |
|---|---|---|
| Sedentary | 1.0 – 1.39 | Daily living, little deliberate exercise |
| Low active | 1.4 – 1.59 | Plus about 30–60 minutes of moderate activity |
| Active | 1.6 – 1.89 | Plus an hour or more of moderate activity |
| Very active | 1.9 – 2.5 | Physically demanding work, or hard training most days |
If what you want is an intake range rather than an expenditure estimate, the calorie intake calculator starts from this same equation and goes one step further.
For coaches
A defensible start, then evidence
Within three weeks the client's own data tells you more than any equation.
- Set a target from the estimate
- A starting point, not a plan.
- Watch the trend
- Weight and adherence across weeks.
- Adjust on what happened
- Not on what should have.
Limits
What this does not tell you
- It is a prediction from height, weight, age, and sex only. It knows nothing about your body composition, so it reads low for very lean bodies and high for very heavy ones.
- Published accuracy is roughly within 10% for most healthy adults, which on a 1,600 kcal estimate is a band of about 320 kcal.
- It was derived on healthy adults. Thyroid conditions, some medications, and a long history of dieting all move resting metabolism away from what the equation predicts.
- The activity multiplier is a band, not a measurement. Two people who both call themselves active can differ by several hundred calories a day.
- It is not a calorie target, and it should never be eaten to.
Sources
- Mifflin MD et al. (1990) — A new predictive equation for resting energy expenditure in healthy individuals
- NCBI Endotext — Estimating energy requirements
- Institute of Medicine — Dietary Reference Intakes for energy and macronutrients
- Ages supported
- adults aged 20 and over
- Formulas and sources last reviewed
Keep reading
- Calorie intake calculatorEstimated maintenance plus a conservative starting range for losing, maintaining, or gaining, with the maths shown.
- BMI calculatorWork out an adult BMI in metric or imperial, with the category and the healthy weight range for your height.
- NutritionMeal options that all hit the same targets, switched on per client, logged against a 300,000-food library.
- Check-insBuild the form once, schedule it, and get each response back with the changes laid out and a draft reply to edit.
A number is a start. Coaching is the rest.
Straton keeps a client's targets, their logs, and their check-ins in one record, so an estimate turns into something you can adjust week to week.