Basal metabolic rate (BMR) is the number of calories your body burns at complete rest to keep essential functions running — breathing, circulation, cell repair and brain activity. It is measured after an overnight fast in a thermally neutral environment, and for most adults it accounts for 60 to 70 percent of total daily energy expenditure.

What is the difference between BMR and TDEE?

BMR is what you burn at rest. TDEE — total daily energy expenditure — is BMR multiplied by an activity factor to account for movement, training and the energy cost of digesting food. TDEE is the number you eat against: eat below it to lose weight, above it to gain. BMR on its own is a baseline, not a calorie target.

Which BMR formula is the most accurate?

For most people, the Mifflin-St Jeor equation is the most accurate of the three and is the one the American College of Sports Medicine recommends as a default. If you know your body fat percentage from a reliable measurement such as a DEXA scan, Katch-McArdle is usually more accurate for lean and athletic people because it works from lean body mass. The revised Harris-Benedict equation tends to read slightly higher than Mifflin-St Jeor.

How accurate is a BMR calculator?

A BMR calculator estimates from population averages, so it is typically accurate to within about 10 percent for a given individual. That is a swing of roughly 150 to 200 calories a day for most adults. The only way to measure BMR precisely is indirect calorimetry in a lab. Treat the number as a starting point, track your weight over two to three weeks, and adjust based on what actually happens.

Why does this calculator ask for my sport?

Generic calculators offer five activity levels, which means a club cricketer training twice a week and a marathon runner in a peak block both tick 'moderately active' and receive the same multiplier. Different sports have substantially different metabolic costs, so this calculator maps your sport and training frequency onto a more specific multiplier derived from published MET values.

Does BMR decrease with age?

Yes. BMR declines gradually from around age 20, largely because lean muscle mass tends to decrease over time and muscle is more metabolically active than fat. Resistance training slows this decline by preserving lean mass, which is one reason strength work is recommended alongside cardiovascular exercise as people get older.

Can you increase your BMR?

To a limited degree. Building lean muscle raises BMR because muscle tissue burns more calories at rest than fat tissue, though the effect is modest — roughly 13 calories per kilogram of muscle per day. Severe or prolonged calorie restriction can lower BMR through metabolic adaptation, which is one reason very aggressive deficits tend to backfire.

What is the lowest number of calories I should eat?

General clinical guidance is not to go below roughly 1,500 calories a day for men and 1,200 for women without medical supervision. Below those levels it becomes difficult to meet micronutrient needs, and the risk of losing lean muscle alongside fat rises sharply. This calculator applies those floors automatically and tells you when it has done so.

BMR Calculator

Work out your basal metabolic rate and daily calorie needs using three validated equations — with activity multipliers tuned to the sport you actually play, rather than a generic five-step guess.

Last reviewed 11 September 2026 · Equations sourced from peer-reviewed literature — see the formulas

Age

Weight (kg)

Height (cm)

Your main sport

Training frequency

Batting and fielding are intermittent, so a match burns less than its duration suggests. Net sessions and bowling spells push this higher.

Formula

The equation the American College of Sports Medicine recommends as the default. Validated against indirect calorimetry in healthy adults and accurate to roughly ±10% for most people.

Fill in your age, height and weight to get:

Your BMR — calories burned at complete rest
Your TDEE — what you actually burn, adjusted for your sport
Five daily targets — for losing, maintaining or gaining weight
A macro split — protein, carbs and fat in grams

Example

A 28-year-old man, 70 kg, 175 cm, playing cricket 3–4 days a week, has a BMR of 1,659 kcal and a TDEE of 2,488 kcal per day.

To lose about 0.5 kg a week he would eat 1,988 kcal a day; to gain at the same rate, 2,988 kcal.

Nothing is saved or sent anywhere — the maths runs entirely in your browser.

What is BMR?

Your basal metabolic rate is the energy your body spends doing nothing at all. Breathing, pumping blood, maintaining body temperature, repairing cells, running your brain — all of it costs calories, and all of it continues whether you get out of bed or not.

For most adults, BMR accounts for 60–70% of total daily energy expenditure. That is the single most useful thing to understand about it: the majority of the calories you burn in a day have nothing to do with exercise. This is why adding a workout to an unchanged diet produces smaller results than people expect, and why very low-calorie diets are counterproductive — they push the body to reduce the largest component of your burn.

BMR is often used interchangeably with RMR (resting metabolic rate), but they are not identical. True BMR is measured under strict conditions — after an overnight fast, following eight hours of sleep, lying still in a thermally neutral room. RMR is measured under less restrictive conditions and typically reads about 10% higher. Every online calculator, this one included, estimates rather than measures.

BMR vs TDEE: which number should you eat against?

This trips up most people who find a BMR calculator. Do not eat at your BMR. BMR is what a body in a coma burns. The number you eat against is TDEE — total daily energy expenditure — which is BMR multiplied by an activity factor.

TDEE has four components:

BMR — 60–70% of the total.
Thermic effect of food — roughly 10%, the energy used digesting and absorbing what you eat. Protein costs the most to process.
Exercise activity — deliberate training. Usually smaller than people assume.
Non-exercise activity thermogenesis (NEAT) — walking, fidgeting, standing, everything else. Varies enormously between individuals and is often larger than the exercise component.

The three formulas, and when to use each

This calculator gives you all three so you can compare. Here is exactly what each one computes.

1. Mifflin-St Jeor — recommended default

Published in 1990 and validated against indirect calorimetry. The American College of Sports Medicine recommends it as the default for healthy adults, and it outperforms Harris-Benedict in most comparison studies.

Men:   BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) + 5
Women: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) − 161

2. Revised Harris-Benedict

The original Harris-Benedict equation dates to 1919; this is the 1984 Roza & Shizgal revision. Still common in clinical settings, though it tends to read slightly higher than Mifflin-St Jeor.

Men:   BMR = 88.362 + (13.397 × weight kg) + (4.799 × height cm) − (5.677 × age)
Women: BMR = 447.593 + (9.247 × weight kg) + (3.098 × height cm) − (4.330 × age)

3. Katch-McArdle — best for lean and athletic people

The only one of the three that accounts for body composition. Because it works from lean body mass, it does not penalise a muscular athlete the way weight-based formulas do. The catch: it is only more accurate if your body fat percentage is genuinely measured. A guess makes it less accurate than Mifflin-St Jeor, not more.

Lean body mass (LBM) = weight kg × (1 − body fat % ÷ 100)
BMR = 370 + (21.6 × LBM)

Activity multipliers by sport

Standard calculators offer five activity levels. The problem is that they collapse genuinely different training loads into the same bucket — a cricketer playing a weekend match and a swimmer doing five pool sessions both land on “moderately active” and get an identical multiplier, despite burning several hundred calories a day apart.

The table below shows the multipliers this calculator uses, derived from published MET values in the Compendium of Physical Activities and weighted for how much of a typical session is actually spent moving.

Sport	1–2 days	3–4 days	5+ days
Cricket	×1.375	×1.5	×1.65
Badminton	×1.45	×1.6	×1.75
Football	×1.45	×1.625	×1.8
Running	×1.45	×1.65	×1.85
Swimming	×1.45	×1.625	×1.8
Basketball	×1.45	×1.625	×1.8
Tennis	×1.425	×1.575	×1.725
Cycling	×1.425	×1.6	×1.8
Gym / strength training	×1.375	×1.5	×1.65

For reference, the generic scale these map onto: Sedentary ×1.2, Lightly active ×1.375, Moderately active ×1.55, Very active ×1.725, Extra active ×1.9.

How accurate is this, really?

Every BMR equation is a regression fitted to a population. Yours is an individual body, so expect the estimate to be within about ±10% — a spread of roughly 150–200 calories a day for most adults. The equations are least reliable at the extremes: very muscular people, people with obesity, and people over about 70.

Use the number as a starting point, not a verdict. Eat at the suggested target for two to three weeks while tracking body weight at a consistent time of day, then adjust by 100–200 calories based on the trend. Your own data beats any formula within a month.

Medical note. This tool provides general fitness information, not medical advice. If you are pregnant or breastfeeding, managing a condition such as diabetes or thyroid disease, recovering from an eating disorder, or under 18, speak to a doctor or registered dietitian before acting on these numbers.

Frequently asked questions

What is BMR?: Basal metabolic rate (BMR) is the number of calories your body burns at complete rest to keep essential functions running — breathing, circulation, cell repair and brain activity. It is measured after an overnight fast in a thermally neutral environment, and for most adults it accounts for 60 to 70 percent of total daily energy expenditure.
What is the difference between BMR and TDEE?: BMR is what you burn at rest. TDEE — total daily energy expenditure — is BMR multiplied by an activity factor to account for movement, training and the energy cost of digesting food. TDEE is the number you eat against: eat below it to lose weight, above it to gain. BMR on its own is a baseline, not a calorie target.
Which BMR formula is the most accurate?: For most people, the Mifflin-St Jeor equation is the most accurate of the three and is the one the American College of Sports Medicine recommends as a default. If you know your body fat percentage from a reliable measurement such as a DEXA scan, Katch-McArdle is usually more accurate for lean and athletic people because it works from lean body mass. The revised Harris-Benedict equation tends to read slightly higher than Mifflin-St Jeor.
How accurate is a BMR calculator?: A BMR calculator estimates from population averages, so it is typically accurate to within about 10 percent for a given individual. That is a swing of roughly 150 to 200 calories a day for most adults. The only way to measure BMR precisely is indirect calorimetry in a lab. Treat the number as a starting point, track your weight over two to three weeks, and adjust based on what actually happens.
Why does this calculator ask for my sport?: Generic calculators offer five activity levels, which means a club cricketer training twice a week and a marathon runner in a peak block both tick 'moderately active' and receive the same multiplier. Different sports have substantially different metabolic costs, so this calculator maps your sport and training frequency onto a more specific multiplier derived from published MET values.
Does BMR decrease with age?: Yes. BMR declines gradually from around age 20, largely because lean muscle mass tends to decrease over time and muscle is more metabolically active than fat. Resistance training slows this decline by preserving lean mass, which is one reason strength work is recommended alongside cardiovascular exercise as people get older.
Can you increase your BMR?: To a limited degree. Building lean muscle raises BMR because muscle tissue burns more calories at rest than fat tissue, though the effect is modest — roughly 13 calories per kilogram of muscle per day. Severe or prolonged calorie restriction can lower BMR through metabolic adaptation, which is one reason very aggressive deficits tend to backfire.
What is the lowest number of calories I should eat?: General clinical guidance is not to go below roughly 1,500 calories a day for men and 1,200 for women without medical supervision. Below those levels it becomes difficult to meet micronutrient needs, and the risk of losing lean muscle alongside fat rises sharply. This calculator applies those floors automatically and tells you when it has done so.

Know your numbers. Now find people to train with.

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