BMR Calculator
Work out your basal metabolic rate — the calories your body burns just staying alive — and see what that becomes once your activity level is added on top.
Fill in the fields to see your result.
What BMR actually measures
Your basal metabolic rate is the energy your body spends doing nothing at all — lying still, awake, in a comfortable room, several hours after eating. It pays for breathing, circulating blood, running your brain, repairing tissue and holding your temperature steady. Even at complete rest, that's the majority of what you burn in a day.
For most people BMR accounts for around 70% of daily energy use. Physical activity is roughly 20%, and digesting food takes the remaining 10% or so. That's worth sitting with for a second: the largest part of your calorie burn happens whether you exercise or not.
The three formulas
All three take your weight in kilograms (W), height in centimetres (H) and age in years (A). The calculator converts for you if you're working in feet and pounds.
Mifflin-St Jeor (1990) — the default
The most widely used equation today, and generally regarded as the most accurate of the three for the general population. If you have no reason to pick another one, use this.
Revised Harris-Benedict (1984)
The original was published in 1919 and revised in 1984. It held the field until Mifflin-St Jeor arrived, and plenty of older training plans still quote it, which is why it's here.
Katch-McArdle
The only one of the three that cares what your weight is made of. Because it works from lean mass, it doesn't need your height, age or sex at all — and it's noticeably more accurate for lean, muscular people, who the other two tend to underestimate. The catch is that it's only as good as your body fat figure, so don't guess.
Turning BMR into daily calories
BMR on its own isn't a target. To get what you actually need in a day, multiply it by an activity factor:
| Activity level | Multiplier |
|---|---|
| Sedentary — little or no exercise | × 1.2 |
| Light — exercise 1–3 times a week | × 1.375 |
| Moderate — exercise 4–5 times a week | × 1.55 |
| Very active — intense exercise 6–7 times a week | × 1.725 |
| Extra active — very intense daily, or a physical job | × 1.9 |
The result is your total daily energy expenditure, or TDEE — the number to plan meals around. The panel above works all five out for you.
How much to trust the number
These equations describe averages, and people are not averages. A 2005 review of the research found that roughly a quarter of the variation in BMR between individuals isn't explained by height, weight, age and sex at all — it comes down to differences in organ size, hormones, genetics and things nobody has cleanly measured.
So treat the output as a well-informed starting estimate, not a fact about your body. The practical approach is to eat at the number for two or three weeks, track what actually happens to your weight, and adjust from there. Reality beats the formula every time.
Frequently asked questions
What is the difference between BMR and TDEE?
BMR is what your body burns doing absolutely nothing — lying still, awake, not digesting. It covers breathing, circulation, brain function and keeping you warm. TDEE is BMR plus everything else you do: walking, working, training, even fidgeting. TDEE is always the bigger number and it's the one to use for planning what you eat. BMR is the foundation it's built on.
Which formula should I choose?
Mifflin-St Jeor for almost everyone — it dates from 1990, it's the one most dietitians reach for, and it's generally considered the most accurate of the three for the general population. Choose Katch-McArdle only if you genuinely know your body fat percentage, because it works from lean mass instead of total weight and is more accurate for lean, muscular people. Harris-Benedict is here mainly because it's the classic and some plans still quote it.
Why does my BMR seem low?
BMR falls with age, with lower body weight and with less muscle, so a smaller or older person will see a smaller number and that's normal. Bear in mind too that these are population averages — a 2005 review found around a quarter of the variation in BMR between people simply isn't explained by height, weight, age and sex. Two people with identical inputs can genuinely differ by a few hundred calories.
Should I eat only my BMR?
No. BMR is what you'd burn in a coma, not a target. Eating at your BMR while living a normal life means a substantial daily deficit, which is more aggressive than most people intend and harder to sustain than it looks. Use your TDEE as the starting point and take a moderate deficit from there if you want to lose weight.
Does BMR change if I diet?
Yes, in two ways. Losing weight lowers BMR simply because there is less of you to maintain. On top of that, prolonged severe restriction can suppress metabolic rate further — the body adapting to less energy coming in. This is one reason very aggressive diets tend to stall, and why a moderate deficit usually wins over time.
Are my numbers sent anywhere?
No. Everything is worked out inside your own browser. Nothing you type is uploaded, stored or shared, and there's no sign-up.
Please note: CalcuLane gives estimates for general information only and is not medical advice, a diagnosis or a treatment plan. BMR equations are population averages and individual metabolic rates vary considerably. Formulas used are Mifflin-St Jeor (1990), the revised Harris-Benedict (1984) and Katch-McArdle. Speak to a doctor or registered dietitian before making significant changes to what you eat.