BMR Calculator (Basal Metabolic Rate)

What is BMR?

BMR (Basal Metabolic Rate) is the number of calories your body uses at complete rest — breathing, circulating blood, regulating temperature, and maintaining organ function — with no physical activity whatsoever. It represents 60–70% of your total daily energy expenditure. The remaining 20–30% comes from physical activity, and 5–10% from the thermic effect of food (TEF).

The Mifflin-St Jeor Formula

Developed in 1990, Mifflin-St Jeor is the most accurate formula for most people — roughly 5% closer to real measured resting metabolic rate than the original Harris-Benedict equations:

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

Example: a 30-year-old man, 175 cm, 70 kg:

BMR = (10 × 70) + (6.25 × 175) − (5 × 30) + 5 = 700 + 1093.75 − 150 + 5 = 1648.75 kcal

From BMR to TDEE (Total Daily Energy Expenditure)

BMR is just your resting burn. Multiply it by an activity factor to get your real daily calorie target:

• Sedentary (desk job, little movement) — BMR × 1.2
• Lightly active (1–3 light workouts/week) — × 1.375
• Moderately active (3–5 workouts/week) — × 1.55
• Very active (6–7 intense sessions/week) — × 1.725
• Extra active (athlete, physical labour, 2× daily) — × 1.9

For a goal-adjusted target (weight loss, maintenance, or muscle gain) use our Daily Calorie Calculator.

What affects BMR?

• Muscle mass: Muscle burns ~3× more calories than fat at rest. Resistance training raises BMR over time.
• Age: BMR falls ~2–3% per decade, mainly due to muscle loss (sarcopenia).
• Sex: Men typically have more muscle, so BMR is 5–10% higher for the same height and weight.
• Thyroid function: Hyperthyroidism raises BMR; hypothyroidism lowers it.
• Genetics: Natural individual variation of 5–10% exists.
• Ambient temperature: Cold environments raise BMR as the body produces extra heat.

How to raise your BMR

1. Resistance training 2–3× per week — builds muscle, which raises resting burn for years.
2. Adequate protein (1.6–2.2 g/kg/day) — supports muscle building; protein also has the highest thermic effect (20–30% of calories burned during digestion).
3. 7–9 hours sleep — maintains leptin, ghrelin, and growth-hormone balance.
4. Avoid extreme calorie cuts — sustained restriction below BMR triggers adaptive thermogenesis: the body lowers its own resting burn.
5. HIIT cardio — elevated post-exercise oxygen consumption (EPOC) extends calorie burn for hours after training.

Not medical advice. If you experience unexplained fatigue, rapid weight change, or suspect a thyroid issue, consult a doctor before adjusting your intake.