BMR Calculator

What is BMR?

A BMR calculator estimates your Basal Metabolic Rate — the number of calories your body burns in 24 hours doing absolutely nothing: no walking, no digesting, no thinking hard. Just the cost of staying alive: breathing, circulating blood, keeping your brain and organs running, repairing cells.

For most people BMR accounts for roughly 60–70% of all calories burned in a day, which makes it the foundation of every calorie plan. Your total daily burn (TDEE) is simply BMR plus everything else — movement, exercise and digestion.

How it works

This calculator uses the Mifflin-St Jeor equation (1990), which research has repeatedly found more accurate than older formulas for the general population:

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

Notice the patterns the formula captures: heavier and taller bodies burn more; each year of age shaves off about 5 kcal/day (metabolism slows as we age); and men burn slightly more than women at the same size, mostly because of greater average muscle mass.

How to use this calculator

1. Enter your age, gender, weight (kg) and height (cm).
2. Read your BMR in kcal/day.
3. Remember: this is your at-rest number. To find how much you can actually eat, multiply by an activity factor (1.2 sedentary up to 1.9 very active) — or use the calorie calculator, which does it for you.

Worked example

A 30-year-old man, 70 kg, 175 cm:

BMR = 10 × 70 + 6.25 × 175 − 5 × 30 + 5
= 700 + 1,093.75 − 150 + 5 = 1,649 kcal/day

So even lying in bed all day, his body would use about 1,650 kcal. A 28-year-old woman at 60 kg and 165 cm: 600 + 1,031.25 − 140 − 161 = 1,330 kcal/day.

Limitations and tips

• BMR is not your food budget: the classic mistake is eating at BMR while living an active life — that is a crash diet. BMR is the floor; your real needs are higher.
• Muscle raises BMR: two people of identical weight can differ by hundreds of calories if one is muscular. Strength training is the most reliable way to nudge BMR upward.
• Estimates vary ±10%: genetics, hormones, thyroid function and medical conditions all move the real number. Use the result as a baseline and adjust from real-world weight trends.
• Age effect is real but slow: the "−5 per year" looks small, but over a decade it is 50 kcal/day — roughly the calories in half a banana — which is why weight creeps up unnoticed with age.