What BMR actually is
BMR is the number of calories your body burns doing absolutely nothing — lying still, awake, at a comfortable temperature. Heart beating, lungs breathing, kidneys filtering. That’s it. No movement, no digestion, no activity.
For a 70 kg, 170 cm, 30-year-old Indian male, BMR is roughly 1,695 calories. He burns that many calories just existing. Everything on top — walking to the kitchen, sitting at a desk, going to the gym — gets multiplied through the activity factor to give TDEE (total daily energy expenditure).
Mifflin-St Jeor vs Harris-Benedict
This calculator uses Mifflin-St Jeor (1990), which is more accurate for most people than the older Harris-Benedict equation (1919). A 2005 meta-analysis in the Journal of the American Dietetic Association found Mifflin-St Jeor predicted measured resting metabolic rate within 10% for 82% of subjects — versus 66% for Harris-Benedict.
The formulas:
Male: BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age) + 5
Female: BMR = (10 × weight in kg) + (6.25 × height in cm) - (5 × age) - 161
Activity multipliers
The five levels here are based on the Katch-McArdle and Harris-Benedict activity classifications. Sedentary (1.2) covers people with desk jobs who don’t exercise. Very active (1.9) applies to athletes training twice a day or people with physically intensive jobs like construction. Most urban Indians land in the 1.375 to 1.55 range.
Overestimating your activity level is the most common mistake. If you think you’re “moderate” but actually walk less than 5,000 steps and exercise twice a week, you’re probably “light.” The multiplier difference between light and moderate is about 180 calories per day — enough to matter over months.
Using BMR for fat loss
To lose approximately 0.5 kg per week, create a 500 calorie/day deficit from TDEE. The calculator shows this as “to lose 0.5 kg/week.” Going below BMR is not recommended — it slows metabolism and loses muscle mass. The calorie deficit calculator gives a more detailed breakdown with macros.
For muscle gain, a 300–500 calorie surplus above TDEE combined with progressive resistance training is the standard approach.
Sources
- Mifflin MD et al. — “A new predictive equation for resting energy expenditure in healthy individuals,” American Journal of Clinical Nutrition, 1990
- Frankenfield D et al. — “Comparison of predictive equations for resting metabolic rate in healthy non-obese and obese adults,” Journal of the American Dietetic Association, 2005
- Indian Council of Medical Research (ICMR) — Nutrient Requirements for Indians, 2020: energy requirement estimates for Indian adults