BMR Calculator
Calculate your basal metabolic rate — the calories your body burns at rest.
1,370 kcal/day
About this calculator
What Is BMR?
Your basal metabolic rate (BMR) is the number of calories your body burns at complete rest — just to keep you alive. It covers the work of the heart, brain, kidneys, liver, lungs, nervous system and muscles while you are awake, relaxed, comfortably warm and not digesting food. Think of it as the fuel an idling car burns while parked. For most people BMR accounts for roughly 60%–70% of total daily calorie use, making it the biggest part of your energy budget. This BMR calculator estimates it from your age, sex, height and weight.
How BMR Is Calculated
Several equations exist. The Mifflin–St Jeor formula is widely regarded as one of the most reliable for modern adults:
- 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 older Harris–Benedict equation and the Katch–McArdle formula (which uses lean body mass) give slightly different results; the Katch–McArdle approach can be more accurate for very lean or very muscular people if you know your body fat.
Worked Example
A 30-year-old woman, 165 cm tall, weighing 65 kg, has a BMR of about 1,370 calories/day. At light activity, that scales up to roughly 1,884 calories/day of total daily energy expenditure; at very active, roughly 2,364.
From BMR to Daily Calorie Needs
Multiply your BMR by an activity factor to estimate the calories you need to maintain your weight: about 1.2 if you are sedentary, 1.375 for light exercise, 1.55 for moderate exercise, 1.725 for hard exercise and 1.9 for very intense training or a physical job. Eating below that number leads to gradual weight loss; above it, to weight gain. The Calorie Calculator does this multiplication for you.
What Affects Your BMR
- Body size and composition: bigger bodies and more muscle burn more at rest.
- Age: BMR tends to decline gradually as muscle mass drops.
- Sex: men usually have a higher BMR than women of the same weight.
- Genetics, hormones and temperature: thyroid levels, pregnancy and a very hot or cold environment all play a role.
Keeping Your Metabolism Healthy
Building and keeping muscle through strength training, getting enough protein and sleep, and avoiding severe crash diets are the best-supported ways to protect your resting metabolism. Treat any calculated BMR as an estimate and adjust based on real-world results. Also see your body fat estimate to understand your composition.
Worked example
A 30-year-old woman at 165cm and 65kg has a BMR of about 1,370 kcal/day — the energy her body burns at complete rest, before any activity is added on top.
Frequently asked questions
What exactly is BMR?
Basal metabolic rate: the calories your body needs just to keep basic functions running — breathing, circulation, cell repair — while completely at rest. It's the floor, not your total daily burn.
How is this different from the Calorie Calculator?
This shows BMR on its own, plus a quick reference for common activity levels. The Calorie Calculator asks for your specific activity level up front and returns one tailored maintenance-calorie number.
Why does BMR decrease with age?
Muscle mass and metabolic activity tend to decline with age, and the Mifflin-St Jeor formula reflects that with an age term — all else equal, an older adult has a somewhat lower BMR than a younger one.
