BMR & Daily Calorie Calculator

From your details to a daily estimate

1. Your detailsAge, sex, weight and height
2. Estimated BMREnergy use at rest
3. Activity levelA rough daily multiplier
4. Estimated TDEEEnergy use across the day

What is basal metabolic rate?

Basal metabolic rate, usually shortened to BMR, describes the energy needed to sustain essential functions under resting conditions. Breathing, circulating blood and regulating temperature all require energy, even when you are not exercising. The unit kcal means kilocalories: the “calories” commonly shown on food labels.

This calculator estimates resting energy needs from a small set of measurements. It does not measure metabolism. Strictly, basal metabolic rate is measured under tightly controlled conditions; resting energy expenditure uses less restrictive conditions. The Mifflin–St Jeor study predicts resting energy expenditure. Online calculators commonly group these estimates under “BMR”, but the terms are not identical.

A BMR estimate is not your full daily energy requirement and should not be treated as a minimum or maximum food allowance. It is one part of an educational model of energy expenditure.

How do the two equations work?

Both methods combine weight in kilograms, height in centimetres and age in years. A different constant or set of coefficients is used for each sex option. When you calculate a result, open “How was my result calculated?” to see your measurements substituted into both equations, followed by the individual terms and activity multiplication.

For Mifflin–St Jeor, the male equation is 10 × weight + 6.25 × height − 5 × age + 5. The female equation uses −161 instead of +5. Revised Harris–Benedict uses 88.362 + 13.397 × weight + 4.799 × height − 5.677 × age for males, and 447.593 + 9.247 × weight + 3.098 × height − 4.330 × age for females.

Imperial measurements are converted before either equation is applied. One stone equals 6.35029318 kg; one pound equals 0.45359237 kg. One foot contains 12 inches, and one inch equals 2.54 cm. The calculator keeps full precision internally and rounds final displayed energy estimates to whole calories. Some displayed intermediate workings are shortened for readability.

Why do the two formulas give different answers?

The equations were developed using different research populations and statistical models. Their coefficients give weight, height and age different mathematical influences. A gap between their answers is therefore expected, rather than proof that you entered something incorrectly. Neither equation is definitively correct for every person.

Comparing the results helps show the uncertainty involved in prediction. The range displayed here simply spans the two calculated TDEE estimates. It is not a measured range, a statistical confidence interval or a promise that your actual energy use lies between its endpoints. Laboratory methods, such as indirect calorimetry, can provide a more direct assessment of resting energy expenditure when clinically appropriate.

How does activity affect daily calorie requirements?

Total daily energy expenditure, or TDEE, estimates energy used over a complete day. Alongside resting energy needs, this includes normal movement, work, exercise and the energy involved in digestion. In this simplified calculator, TDEE equals the resting estimate multiplied by the selected activity factor. The factor is intended to represent the overall daily allowance; do not add a second allowance for digestion or an exercise session to this result.

The descriptions are broad guides. Two people who exercise three times a week may have different daily needs if one has a seated job and the other is on their feet all day. Session duration, effort, recovery and everyday movement also matter. Consider your overall routine rather than choosing a category from exercise frequency alone.

Your activity and energy expenditure can change between days. Try another activity selection and recalculate to explore the effect on the model. That comparison teaches the influence of the multiplier; it does not tell you exactly how much food to eat on a particular day.

Using the calculator as a learning tool

Start with accurate measurements in your preferred units. Select the equation sex option and a typical activity level, then calculate. Compare the two resting estimates before looking at the daily range. Finally, expand the working and follow each multiplication and addition. Ask which inputs have changed if you repeat the exercise.

For teaching, use a fictional example rather than asking learners to share personal measurements. For instance, an 80 kg, 180 cm, 35-year-old male gives a Mifflin–St Jeor estimate of 1,755 kcal/day and a revised Harris–Benedict estimate of approximately 1,825 kcal/day. Exploring the working is more valuable than treating either number as a precise physiological measurement.

“Start Again” clears the details and results. This tool does not save a personal profile or send entered figures to a server. The surrounding website may have its own cookie settings, but the calculator runs in an isolated frame that keeps its form values out of the parent page.

Research behind the equations

• Mifflin and colleagues (1990): A new predictive equation for resting energy expenditure in healthy individuals.
• Roza and Shizgal (1984): The Harris Benedict equation reevaluated.
• Maastricht University Medical Center: calculating energy expenditure and the revised coefficients.

Equations and supporting sources checked 15 September 2026. Activity factors are simplified teaching assumptions rather than a separate personalised assessment.