If you've ever Googled "calorie calculator" you've probably hit two acronyms that sound interchangeable: BMR and TDEE. They're not the same, and using the wrong one is the most common mistake in DIY calorie planning. Here's the difference in plain English.
The 30-second answer
- BMR = calories you burn doing absolutely nothing (basal metabolism only)
- TDEE = calories you burn on a typical day (BMR + walking, working, exercising, fidgeting)
For weight planning, you almost always want TDEE.
BMR explained
Basal Metabolic Rate is the energy your body uses for "keeping the lights on" — heart, lungs, brain, kidneys, cell repair, body temperature. If you lay in bed all day without moving, BMR is what you'd burn.
Typical BMR figures for UK adults:
- Average woman: 1,300–1,500 kcal
- Average man: 1,600–1,900 kcal
TDEE explained
Total Daily Energy Expenditure is what you actually burn when you live a normal life. It's BMR plus:
- NEAT (Non-Exercise Activity Thermogenesis) — fidgeting, walking to the kettle, climbing stairs
- Exercise — deliberate workouts
- TEF (Thermic Effect of Food) — calories used digesting what you eat (~10% of intake)
To get TDEE from BMR, multiply by an activity factor:
| Lifestyle | Multiplier |
|---|---|
| Mostly seated (desk job, no exercise) | BMR × 1.2 |
| Lightly active (light exercise 1–3 days/week) | BMR × 1.375 |
| Moderately active (3–5 days/week) | BMR × 1.55 |
| Very active (6–7 days/week) | BMR × 1.725 |
| Athlete-level (twice-daily training) | BMR × 1.9 |
Which one do I use for...?
Losing weight
Use TDEE, then subtract 500–600 kcal. That's your daily target.
Example: TDEE 2,200 → eat 1,600–1,700 kcal to lose ~1 lb/week.
Maintaining weight
Use TDEE. That's your maintenance number — eat that much and you'll stay roughly stable.
Gaining muscle
Use TDEE, then add 250–500 kcal. That's your bulk target.
Example: TDEE 2,200 → eat 2,450–2,700 kcal to gain ~0.5 lb/week.
Setting a minimum floor
Use BMR. Most dietitians advise never eating below your BMR for more than a few days at a time — your body starts dialling down hormones, mood, energy and muscle.
Common mistake: using BMR as your weight-loss target
Plenty of people calculate their BMR (say 1,500 kcal) and then try to eat that. The result: a deficit so aggressive their body fights back with cravings, low mood and stalled progress.
If your TDEE is 2,300 and you eat at BMR (1,500), you're running an 800-calorie daily deficit. That's near the upper safe limit, and very few people sustain it for long. Eat at TDEE − 500 instead.
Worked example end-to-end
James is 38, 6'0" (183cm), 15 stone (95kg), works at a desk and goes to the gym twice a week.
- BMR (Mifflin–St Jeor): (10 × 95) + (6.25 × 183) − (5 × 38) + 5 = 950 + 1,144 − 190 + 5 = 1,909 kcal
- Activity multiplier: 1.375 (light)
- TDEE: 1,909 × 1.375 = 2,625 kcal
- Weight-loss target: 2,625 − 600 = 2,025 kcal/day
James eats 2,025 kcal a day, loses about 1 lb a week, and never dips below his 1,909 BMR floor. Sustainable.
The bottom line
BMR is your "engine running" cost. TDEE is your actual daily burn. For weight loss, gain or maintenance, use TDEE — and never park your daily intake below your BMR for long.
Sources: British Dietetic Association, Mifflin–St Jeor equation (1990), NHS Eatwell guidance.