BMI vs BMR vs TDEE: Which Number Should You Use?

BMI, BMR, and TDEE show up in almost every fitness article — and they answer different questions. Mixing them up leads to bad calorie targets and confusing progress checks.

BMI (body mass index) is a height-and-weight ratio. It is a population screening tool, not a direct measure of body fat or fitness. Athletes can land in the “overweight” range with low body fat; sedentary people can show a “normal” BMI with high visceral fat.

BMR (basal metabolic rate) estimates calories burned at complete rest. Formulas like Mifflin–St Jeor use sex, age, weight, and height. BMR is the floor of your energy needs — not what you should eat on a training day.

TDEE (total daily energy expenditure) multiplies BMR by an activity factor to estimate maintenance calories. Fat loss usually starts from a modest deficit below TDEE; muscle gain often uses a small surplus.

Practical rule: use BMI as a rough health flag, BMR to understand resting burn, and TDEE to set daily calories. Then refine with waist measurements, strength progress, and how clothes fit — not a single index alone.

TaskEaser’s BMI, BMR, and TDEE calculators run entirely in your browser so you can compare scenarios without creating an account.