What BMR and TDEE Measure
The two numbers that define your daily calorie budget, and the equation behind them.
BMR is standby draw; TDEE is total daily consumption. Mifflin-St Jeor is the regression that turns body stats into both.
Basal Metabolic Rate (BMR) is the energy your body spends keeping you alive at rest — breathing, circulation, cell maintenance. Total Daily Energy Expenditure (TDEE) is BMR multiplied by an activity factor to cover everything else. Mifflin-St Jeor is the equation that turns sex, age, weight, and height into a BMR estimate within about 5% of lab-measured resting metabolism.
Quick answer
BMR is standby draw; TDEE is total daily consumption. Mifflin-St Jeor is the regression that turns body stats into both.
Key points
- ▸ Mifflin-St Jeor male: BMR = 10 × kg + 6.25 × cm − 5 × age + 5. Female: same − 161.
- ▸ Activity multipliers: sedentary 1.2, light 1.375, moderate 1.55, very active 1.725, extreme 1.9.
- ▸ BMR accounts for about 60-75% of TDEE for most adults; the rest is activity and the thermic effect of food.
- ▸ Mifflin-St Jeor replaced Harris-Benedict (1919) as the clinical default because Harris-Benedict over-estimates BMR for sedentary modern populations by 5-10%.
- ▸ The equation assumes average body composition. Very lean or very obese bodies deviate — lean mass burns more per kg than fat mass.
Examples
- 30y female, 65 kg, 165 cm, light activityBMR = 10×65 + 6.25×165 − 5×30 − 161 = 1370 kcal. TDEE = 1370 × 1.375 ≈ 1884 kcal.
- 45y male, 90 kg, 180 cm, sedentaryBMR = 10×90 + 6.25×180 − 5×45 + 5 = 1805 kcal. TDEE = 1805 × 1.2 ≈ 2166 kcal.
- 25y male, 75 kg, 178 cm, very activeBMR ≈ 1723 kcal. TDEE = 1723 × 1.725 ≈ 2972 kcal — the gap between sedentary and very active is nearly 1000 kcal for the same body.
When to use which tool
Related
- Metabolic Floor · BMR / TDEECalculate your Basal Metabolic Rate and Total Daily Energy Expenditure using Mifflin-St Jeor. Power-consumption view with cut / maintain / bulk zones.
- Interpreting Your TDEE ResultOnce you know TDEE, the three calorie zones translate it into a daily target.
- When the BMR Equation BreaksMifflin-St Jeor is a regression on average bodies. Here is where it fails.
Frequently asked questions
› Is BMR the same as RMR? Trust & accuracy
Close but not identical. BMR is measured after an overnight fast in a thermoneutral environment; RMR is measured under less strict conditions and runs about 10% higher. Equation outputs are usually labeled BMR but approximate RMR in practice.
› Do I need to refactor if I lose weight?
Yes. Every 10 kg of weight loss drops BMR by roughly 100 kcal per day via Mifflin-St Jeor. Recompute monthly if you are in an active cut.
› Why does activity multiplier matter so much? Troubleshooting
The multiplier moves TDEE by 700+ kcal between sedentary and very active. Most estimation error comes from over-claiming activity — desk jobs with three gym sessions per week are usually light (1.375), not moderate.
› How should I use this guide with a Kefiw tool? How-to
Use the guide as the plan and the linked Kefiw tool as the check. Read the steps first, try the move manually, then use the tool to compare outputs, catch edge cases, and decide whether the result actually fits your task.
› What mistake do tool guides help avoid? Troubleshooting
Tool guides help avoid using a utility mechanically without understanding what you are trying to accomplish. Most word, writing, and text utilities are fast, but speed can hide context mistakes. Know whether you are solving a puzzle, cleaning copy, drafting a line, or checking a rule.