Your body burns calories around the clock, long before you lace up your running shoes. How many? Two numbers answer it — and confusing them is one of the most common reasons diets fail.
BMR is your idle engine — calories burned lying in bed doing nothing. TDEE is the full-day total: heartbeat, gym, walking the dog. One is survival; the other is real life.
What Is BMR? Your Body’s Idle Engine
Basal Metabolic Rate (BMR) keeps the lights on: breathing, blood, temperature, cell repair. It’s 60–70% of daily burn — your organs are energy hogs (your brain alone uses ~20% of resting calories).
The Mifflin-St Jeor equation (most accurate for the general population):
- Women: 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161
- Men: 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5
What Is TDEE? The Full-Day Total
Total Daily Energy Expenditure (TDEE) = BMR + everything else. Three parts:
1. BMR — the base (60–70%)
The resting burn. The foundation.
2. Activity — the variable (15–30%)
Exercise, walking, fidgeting, chores. The only part you directly control — a warehouse worker and a desk worker with the same body can differ by 500–800 calories/day.
3. Thermic effect of food (~10%)
Digestion costs energy; protein costs most (20–30% of its calories).
BMR → TDEE via an activity multiplier:
- 1.2 — Sedentary: desk job, little exercise
- 1.375 — Lightly active: 1–3 days/week
- 1.55 — Moderately active: 3–5 days/week
- 1.725 — Very active: 6–7 days/week
- 1.9 — Extra active: physical job or 2× daily training
Worked Example
30-year-old woman, 65 kg, 165 cm, moderately active (×1.55):
BMR: 10×65 + 6.25×165 − 5×30 − 161 = 650 + 1,031.25 − 150 − 161 = 1,370 cal/day.
TDEE: 1,370 × 1.55 = 2,124 cal/day — her real maintenance number.
How to Use These Numbers
- Lose weight: TDEE minus 300–500 cal
- Maintain: eat at TDEE
- Gain muscle: TDEE plus 200–300 cal, with strength training
At TDEE 2,124, a 500-cal deficit = ~1,624/day → ~1 lb (0.45 kg) fat loss per week. Never eat below BMR long-term; recalculate every few months as weight changes. BMI is a separate measure — check a BMI calculator for the full picture.
Common Mistakes
Treating BMR as a target. It’s a floor, not a goal. Double-counting exercise — if your multiplier covers activity, don’t add tracker calories on top. Ignoring NEAT — standing vs sitting can be 150–300 cal/day. Set and forget — BMR drops 1–2% per decade after 20; revisit numbers.
Know Your Real Numbers in 30 Seconds
Our free BMR calculator uses Mifflin-St Jeor plus activity multipliers for your TDEE and safe targets.
Plug stats into the free BMR calculator, then the calorie calculator for a day-by-day plan. Browse the Health hub for more.
Frequently Asked Questions
Can I lose weight eating at BMR?
You’d lose, but it’s a floor, not a strategy — no energy for activity or digestion. Eat below TDEE but above BMR.
Why is my TDEE higher than my friend’s at the same weight?
Height, age, sex, muscle, and especially activity differ. Same weight, different lives = several hundred calories apart.
How often recalculate?
Every 2–3 months, or after ±5 kg, activity shifts, or plateaus.
Is a 500-calorie deficit safe?
For most healthy adults, yes (~1 lb/week). Never go below BMR; smaller people may prefer 300.
Are fitness trackers accurate for TDEE?
Roughly — wrist trackers often overestimate exercise calories 20%+. Mifflin-St Jeor with an honest multiplier is usually more reliable.