BMR Calculator
Work out the energy your body spends at complete rest, compared across four published equations, then multiply it through to your total daily burn and the calorie targets that follow from it. Add a body fat percentage to unlock the two lean-mass equations, which are more accurate than anything height and weight alone can produce.
The two equations differ by 47 kcal (2.8%) for you.
Total daily energy expenditure
2556kcal / day
- At rest
- 1649 kcal
- Digestion
- 256 kcal
- Movement
- 651 kcal
All four equations
- Mifflin-St Jeor
- 1649 kcal
- Harris-Benedict (revised)
- 1696 kcal
- Katch-McArdle
- —
- Cunningham
- —
Enter a body fat percentage to see the two lean-mass equations.
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Daily calorie targets
Each row is your total daily expenditure shifted by a fixed amount. A deficit of 500 kcal a day is the conventional figure for losing about half a kilogram, or a pound, of fat a week, because a kilogram of body fat stores roughly 7 700 kcal. The loss rows never drop below a floor of 1 200 kcal, since eating under that makes it very hard to meet protein and micronutrient needs.
| Goal | Adjustment | Daily intake | What it means |
|---|---|---|---|
| Aggressive loss | −1000 kcal | 1556 | About 1 kg / 2 lb a week. Hard to sustain and easy to under-eat protein on. |
| Weight loss | −500 kcal | 2056 | About 0.5 kg / 1 lb a week. The usual recommendation. |
| Mild loss | −250 kcal | 2306 | About 0.25 kg / 0.5 lb a week. Slower, but easier to hold to. |
| Maintenance | TDEE | 2556 | Eat at this to hold your current weight. |
| Mild gain | +250 kcal | 2806 | A lean bulk, paired with resistance training. |
| Weight gain | +500 kcal | 3056 | Faster gain, with more of it as fat. |
Activity multipliers
The multiplier converts BMR into your whole day. It is the least precise part of the calculation, so when two levels both sound like you, take the lower one — over-reporting activity is the single most common reason a calorie target fails to produce the expected weight change.
| Level | Multiplier | Typical week | Your TDEE |
|---|---|---|---|
| Sedentary | ×1.2 | Desk job, little or no deliberate exercise. | 1979 |
| Lightly active | ×1.375 | Light exercise or sport 1–3 days a week. | 2267 |
| Moderately active | ×1.55 | Moderate exercise or sport 3–5 days a week. | 2556 |
| Very active | ×1.725 | Hard exercise 6–7 days a week. | 2845 |
| Extra active | ×1.9 | Physical job, or hard training twice a day. | 3133 |
The four equations
The first two predict resting energy from height, weight, age and sex. The second two work from lean body mass instead, which is why they need a body fat percentage and why they are more accurate when you have one.
Mifflin-St Jeor (1990)
Men: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5 Women: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161
The current clinical default, recommended by the Academy of Nutrition and Dietetics. It was fitted on 498 adults and predicts measured resting energy within 10% in roughly 82% of non-obese and 70% of obese people. Note the age term: a flat 5 kcal per year, regardless of anything else about you.
Harris-Benedict, revised (1984)
Men: BMR = 13.397 × weight + 4.799 × height − 5.677 × age + 88.362 Women: BMR = 9.247 × weight + 3.098 × height − 4.330 × age + 447.593
Roza and Shizgal's revision of the 1919 original. Still widely quoted, and typically a few percent higher than Mifflin-St Jeor — if another calculator gave you a bigger number, it was probably using this.
Katch-McArdle and Cunningham
Lean mass = weight × (1 − body fat % / 100) Katch-McArdle: BMR = 370 + 21.6 × lean mass (kg) Cunningham: RMR = 500 + 22 × lean mass (kg)
Neither uses age, height or sex — all of that information is already carried by lean mass, which is what actually burns the energy. That makes them the better choice for anyone whose composition is unusual for their height and weight, in either direction: a muscular person is under-estimated by the first two equations, and someone with very little muscle is over-estimated. Cunningham was fitted on a more athletic sample, which is why it reads higher.
Where your resting energy actually goes
Organ-level measurements (Elia, 1992) explain why BMR is so hard to move. Your liver and brain each cost about as much at rest as your entire skeletal musculature, and neither responds to training. Muscle only dominates once you start moving — which is a reason to train, but not a reason to expect a large jump in the number above.
| Tissue | Share of BMR | Notes |
|---|---|---|
| Liver | 20% | Highest resting rate per kilogram of any large organ. |
| Brain | 20% | Roughly constant regardless of body size or activity. |
| Skeletal muscle | 20% | At rest only — this share rises sharply during movement. |
| Heart | 9% | Never stops, which is why its small mass costs so much. |
| Kidneys | 8% | Continuous filtration of the entire blood volume. |
| All remaining tissue | 23% | Fat, bone, gut, skin and everything else combined. |
How BMR changes with age
These figures hold height and weight fixed on purpose — men at 178 cm and 75 kg, women at 164 cm and 62 kg — so that the only thing changing down the column is age. The decline is exactly the 5 kcal per year the Mifflin equation subtracts, which is a modelling assumption rather than a measurement. Research published in Science in 2021 found that expenditure adjusted for body composition is broadly stable from about 20 to 60, and that most of what people experience as a slowing metabolism is lost muscle rather than age itself.
| Age | Men | Women |
|---|---|---|
| 20 | 1768 kcal | 1384 kcal |
| 30 | 1718 kcal | 1334 kcal |
| 40 | 1668 kcal | 1284 kcal |
| 50 | 1618 kcal | 1234 kcal |
| 60 | 1568 kcal | 1184 kcal |
| 70 | 1518 kcal | 1134 kcal |
What these numbers cannot tell you
Every equation is a population average
Two people of identical height, weight, age and sex can have measured resting rates 200 to 300 kcal apart. The equations predict the middle of that distribution, not you. Even the best of them lands within 10% only about four times in five — so treat the result as a starting estimate with a band around it, and correct it against real weight change.
Dieting lowers BMR by more than weight loss alone
Sustained energy restriction produces adaptive thermogenesis: resting expenditure falls further than the loss of body mass predicts, and stays suppressed for some time afterwards. This is also why the figure you calculate before a diet is not the figure that applies part-way through one. It is not "starvation mode" in the sense the phrase usually implies, and it does not stop weight loss — but it does mean a deficit shrinks as you go.
Medical conditions move it
Thyroid disorders, fever, major injury, pregnancy, and a number of medications change resting expenditure substantially — often well beyond the accuracy of any prediction equation. None of these are modelled here. If you have a diagnosed condition that affects metabolism, a prediction equation is the wrong tool and indirect calorimetry is the right one.
The activity multiplier is a blunt instrument
A single number between 1.2 and 1.9 stands in for everything you do in a day. Non-exercise activity thermogenesis alone varies by several hundred kcal a day between people of similar size, so two people at the same "moderately active" setting can genuinely differ by more than the gap between two of the levels.
Medical disclaimer. This calculator is for general information and education only. It is not medical advice, not a diagnosis, and not a substitute for professional care. The calorie figures are an estimate, not a prescription. Do not use them to plan intake for a child, during pregnancy or breastfeeding, or alongside an eating disorder or a diagnosed metabolic condition.Speak to a doctor or a registered dietitian before making significant dietary changes.Last reviewed .
Frequently asked questions
What is Basal Metabolic Rate (BMR)?
BMR is the energy your body spends doing nothing at all — keeping your heart beating, your lungs moving, your brain running, your body temperature steady, and your cells repairing themselves. It is measured after a full night’s sleep, lying still, having eaten nothing for twelve hours, in a thermally neutral room. For most people it is 60 to 70% of everything they burn in a day, which is why it is the foundation every calorie target is built on.
What is the difference between BMR and RMR?
RMR — resting metabolic rate — is measured under less strict conditions: at rest, but without the overnight fast and the laboratory protocol. Because of that it comes out roughly 10% higher than true BMR. In practice the two terms are used interchangeably, and the equations here were mostly fitted against RMR measurements despite being called BMR equations. The distinction matters for research, not for setting your calorie intake.
Which BMR formula is the most accurate?
Mifflin-St Jeor, for most people. The Academy of Nutrition and Dietetics recommends it after a systematic review found it predicts measured resting energy within 10% in about 82% of non-obese adults and 70% of obese adults — better than the alternatives that use only height, weight, age and sex. If you know your body fat percentage, Katch-McArdle and Cunningham are usually better still, because they work from lean mass and so do not have to guess at your composition.
Why is Harris-Benedict still shown if Mifflin-St Jeor is better?
The original Harris-Benedict equation dates from 1919 and the revision used here from Roza and Shizgal in 1984. It is still the figure many older references, textbooks and fitness apps quote, so it is shown for comparison — if another calculator gives you a higher number, this is usually why. It tends to overestimate by around 5% against modern populations.
When should I use Katch-McArdle or Cunningham instead?
Both work from lean body mass rather than total weight, so they are the better choice whenever you actually know your body fat percentage — and they are markedly better for anyone whose build is far from average, in either direction. Katch-McArdle is BMR = 370 + 21.6 × lean kg. Cunningham is 500 + 22 × lean kg and was fitted on a more athletic sample, so it reads a few percent higher. Enter a body fat percentage above and both appear.
How do I turn BMR into a daily calorie target?
Multiply BMR by an activity factor to get TDEE, your total daily energy expenditure — 1.2 if you are sedentary, up to 1.9 for an athlete or manual worker. Eating at TDEE holds your weight steady. A deficit of about 500 kcal a day corresponds to roughly half a kilogram, or a pound, of fat a week. The calculator does all of this above, including the deficit and surplus targets.
How accurate is the activity multiplier?
It is the weakest part of the whole estimate, considerably weaker than the BMR equation itself. Most people overestimate how active they are, and non-exercise activity — fidgeting, standing, walking about — varies by several hundred calories a day between people of similar size. Treat the TDEE figure as a starting point, then correct it against real weight change over two to three weeks rather than trusting the first number.
Can I increase my BMR?
A little, and slowly. Adding muscle raises it, but resting muscle burns only about 13 kcal per kilogram per day, so several kilograms of hard-won muscle buys perhaps 50 to 100 kcal a day — real, but not transformative. The larger effects run the other way: severe or prolonged dieting lowers BMR by more than the weight loss alone predicts, an adaptation that persists for a while after you stop. Sleep, illness and thyroid function all move it too.
Does metabolism really slow down with age?
Yes, but less dramatically and later than the folklore suggests. The Mifflin equation subtracts 5 kcal per year of age, so 30 years costs about 150 kcal a day at a fixed height and weight — the table on this page shows exactly that. Large-scale work published in Science in 2021 found that energy expenditure adjusted for body composition is actually stable from roughly age 20 to 60, and only then begins to decline. Most of what people experience as a slowing metabolism is lost muscle and reduced movement.
Is my data saved or uploaded anywhere?
No. Every calculation runs in your browser. Nothing you type is uploaded, stored, or logged, and the page keeps working offline once loaded. If you share the page URL after calculating, the figures you entered are in the link — clear the query string first if you would rather not pass them on.