BMR Calculator
Find your Basal Metabolic Rate — the calories your body burns at complete rest.
The BMR calculator estimates your Basal Metabolic Rate: the energy your body needs just to stay alive at rest — breathing, circulating blood, maintaining temperature. BMR usually accounts for 60–70% of the calories you burn each day, and it is the base for any calorie plan.
How to use the calculator
- Select your gender.
- Enter your age, weight and height.
- The result is the calories you would burn lying still all day.
- Multiply it by an activity factor, or use our calorie calculator, to get your daily needs.
How it is calculated
Men: BMR = 10 × weight + 6.25 × height − 5 × age + 5
Women: BMR = 10 × weight + 6.25 × height − 5 × age − 161
(weight in kg, height in cm)
Worked example
70 kg, 170 cm, age 30, male
BMR = 10(70) + 6.25(170) − 5(30) + 5
BMR = 700 + 1062.5 − 150 + 5 = 1,617.5, so about 1,618 calories/day.
Who should use this calculator
- Anyone planning a calorie target, because BMR is the floor your intake should never sit below for long.
- People who have been eating very little and feel cold, tired and unable to lose weight, and want to understand why.
- Coaches and dietitians estimating a starting point before adjusting for real-world results.
- Anyone curious about how much of their daily energy is spent doing nothing at all.
Common mistakes to avoid
- Confusing BMR with daily calories. BMR is the energy you would burn lying still all day. Once you add walking, working, digesting and exercise, the real number is 20–60% higher.
- Eating below BMR for weeks. Aggressive deficits reduce muscle mass, lower energy and can slow the metabolic rate, making further loss harder rather than easier.
- Assuming BMR is fixed. It falls as you lose weight and as you age, and rises when you add muscle. Recalculate after a significant change in weight.
- Using BMR for athletes. A muscular person burns considerably more at rest than the formula suggests, because muscle tissue is metabolically active.
- Forgetting that estimates carry error. Formulas are typically within about 10% of true needs. Treat the result as a starting point and adjust based on what the scale and tape measure do over two to three weeks.
BMR versus the calories you actually burn
BMR covers only the basics: breathing, circulation, temperature control and cell repair. For a 30-year-old man at 70 kg and 170 cm, that comes to about 1,618 calories a day. Nobody stays at rest for twenty-four hours, so the useful figure is TDEE — BMR multiplied by an activity factor.
At a lightly active level (a workout one to three days a week) the multiplier is about 1.375, which lifts the daily requirement to roughly 2,224 calories. A sedentary office worker might sit closer to 1.2, giving around 1,940. The gap between those two is nearly 300 calories a day — enough to explain why two people of the same size can eat differently and end up at the same weight.
BMR terms explained
- BMR
- Basal Metabolic Rate — the calories burned at complete rest to keep the body functioning.
- RMR
- Resting Metabolic Rate, measured under less strict conditions. It is usually slightly higher than BMR and the two are often used interchangeably.
- Mifflin-St Jeor equation
- The formula this calculator uses. It is considered the most accurate of the simple predictive equations for most adults.
- TDEE
- Total Daily Energy Expenditure — BMR plus every activity of the day, including digesting food and moving around.
- Lean body mass
- Everything in your body except fat. It is the main driver of how much energy you burn at rest.
Habits that protect your metabolic rate
Metabolism is not fixed, and a few habits keep it healthier. Strength training preserves and builds the muscle that drives resting energy use. Eating enough protein does the same job while keeping you full. Sleeping seven to eight hours protects appetite hormones and insulin sensitivity, both of which slip badly with chronic short sleep. And avoiding long stretches on very low calories matters most of all, because severe restriction is what reliably shrinks muscle, energy and the metabolic rate together.
Frequently asked questions
What is the difference between BMR and RMR?
BMR is measured under strict resting conditions, while RMR (Resting Metabolic Rate) is measured under looser conditions and is usually slightly higher. In practice the two are used almost interchangeably.
Can I increase my BMR?
Yes, modestly. Building muscle raises BMR slightly because muscle burns more energy at rest. Eating enough protein, sleeping well and avoiding very-low-calorie diets also help protect your metabolic rate.
Should I eat exactly my BMR?
No. Eating only your BMR would be too little for most people, because you also move, digest food and exercise. Use BMR as a base and multiply by an activity factor to find your maintenance calories.