BMR, TDEE, and Body Fat: The Numbers Behind Your Calorie Goals
June 4, 2026 · 4 min read
If you've ever tried to manage your weight by tracking calories, you've probably run into three numbers: BMR, TDEE, and body fat percentage. They're related, they each mean something specific, and confusing them leads to plans that don't work. This guide explains each one, the math behind it, and how to use the numbers in practice.
BMR: the floor
Basal Metabolic Rate is the number of calories your body burns doing absolutely nothing — heartbeat, breathing, cell maintenance — at complete rest in a temperature-controlled room with no digestion happening. It's the minimum energy your body needs to keep running.
The most widely cited formula is the Mifflin-St Jeor equation (1990), which is more accurate than the older Harris-Benedict equation for most modern adults:
Men: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age(yr) + 5
Women: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age(yr) − 161
A 30-year-old man at 70 kg and 175 cm, for example, has a BMR of about 1,649 kcal/day.
BMR is useful as a reference, but you can't use it directly for calorie planning — nobody is at complete rest all day. That's where TDEE comes in.
TDEE: what you actually burn
Total Daily Energy Expenditure is your actual daily calorie burn, accounting for movement. It's BMR multiplied by an activity factor:
| Level | Factor | Example |
|---|---|---|
| Sedentary | 1.2 | Desk job, little exercise |
| Light | 1.375 | Light exercise 1–3 days/wk |
| Moderate | 1.55 | Exercise 3–5 days/wk |
| Active | 1.725 | Hard exercise 6–7 days/wk |
| Very active | 1.9 | Athlete, physical job + training |
That same 70 kg / 175 cm / 30 yr man at a moderate activity level has a TDEE of approximately 2,556 kcal/day. Eat roughly that much and your weight stays the same.
TDEE is the number you actually plan around:
- To lose fat: eat less than TDEE (a deficit of ~250–500 kcal/day is a common target)
- To gain muscle: eat more than TDEE (a surplus of ~200–300 kcal/day for a "lean bulk")
- To maintain: eat at TDEE
A 500 kcal/day deficit works out to roughly 0.45 kg (1 lb) per week of fat loss, assuming the deficit is real and consistent.
Use the TDEE Calculator to compute your maintenance calories and see the suggested targets for cutting, maintaining, and bulking side by side.
Body fat percentage: a better signal than weight
The scale measures total mass — fat, muscle, water, glycogen, everything. Body fat percentage tells you what fraction of that mass is actually fat, which gives you a cleaner read on body composition.
Common reference ranges (these vary by source — use as a rough guide):
| Category | Men | Women |
|---|---|---|
| Essential | < 6% | < 14% |
| Athletic | 6–14% | 14–21% |
| Fitness | 14–18% | 21–25% |
| Average | 18–25% | 25–32% |
| Above average | > 25% | > 32% |
The most accurate measurements use DEXA or hydrostatic weighing. The U.S. Navy tape method is a practical alternative that needs only a tape measure: it uses your height, neck, waist, and (for women) hip circumference in a logarithmic formula. It's not perfectly accurate, but it's consistent and good enough to track change over time.
Use the Body Fat Calculator for the Navy tape method — enter your measurements in centimeters and it returns your estimated body fat %, your category, and fat and lean mass if you enter your weight.
How the three numbers relate
- BMR × activity factor = TDEE (maintenance calories)
- TDEE ± deficit/surplus = your daily target
- Body fat % tells you the composition of your current weight and helps you gauge progress beyond just the scale
They serve different purposes. A calorie plan built on TDEE tells you how much to eat. Body fat percentage tells you whether your results are moving in the right direction (fat down, lean mass stable or up).
Practical caveats
These formulas are estimates. Individual metabolism varies, activity factors are coarse, and the navy method has error bars of a few percentage points. Don't treat the numbers as ground truth — use them as a starting point, track real results for 2–4 weeks, and adjust.
All three calculators here run entirely in your browser: TDEE Calculator, BMR Calculator, Body Fat Calculator.