Two numbers that decide your calorie target
Almost every diet plan, fitness app and calorie tracker is built on two figures: your Basal Metabolic Rate (BMR) and your Total Daily Energy Expenditure (TDEE). Get these right and weight management becomes arithmetic rather than guesswork. Get them wrong — or copy a generic “2,000 calories a day” figure that was never meant for you — and you will spend weeks wondering why the scale will not move.
BMR is the energy your body burns at complete rest, just to stay alive: heartbeat, breathing, brain activity, maintaining body temperature, repairing cells. TDEE takes that resting figure and scales it up for everything else you do in a day — walking to the kitchen, typing, exercising, even digesting food. TDEE is the number that actually matters for eating, because it is roughly how many calories you burn in total.
How BMR is estimated
The most widely used formula today is the Mifflin-St Jeor equation, published in 1990 and considered more accurate for modern populations than the older Harris-Benedict equation. It uses weight, height, age and sex:
Men: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5Women: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161A 35-year-old man at 80 kg and 180 cm computes as 10×80 + 6.25×180 − 5×35 + 5 = 1,755 calories per day at rest. That is the energy he would burn lying in bed all day — a floor, not a target.
From BMR to TDEE: the activity multiplier
To turn BMR into TDEE you multiply by an activity factor that reflects how much you move. The standard bands are:
| Activity level | Multiplier | Typical week |
|---|---|---|
| Sedentary | × 1.2 | Desk job, little or no exercise |
| Lightly active | × 1.375 | Light exercise 1–3 days |
| Moderately active | × 1.55 | Moderate exercise 3–5 days |
| Very active | × 1.725 | Hard exercise 6–7 days |
| Extra active | × 1.9 | Physical job or twice-daily training |
Our 35-year-old with a BMR of 1,755, working a desk job but training three times a week (moderately active), has a TDEE of about 1,755 × 1.55 ≈ 2,720 calories. That figure — not his BMR — is what he should build a diet around.
Turning TDEE into a goal
Once you know your TDEE, the rest is straightforward energy balance. One pound of body fat stores roughly 3,500 calories, so the classic targets are:
- To lose weight: eat below your TDEE. A deficit of 500 calories a day predicts about one pound of loss per week — aggressive enough to see progress, gentle enough to sustain.
- To maintain: eat at your TDEE. Small natural fluctuations average out.
- To gain muscle: eat slightly above TDEE — a surplus of 250–500 calories — paired with resistance training so the surplus builds muscle rather than only fat.
Two cautions. First, never eat below your BMR for long; it leaves too little energy for basic function. Second, these are estimates. Track your actual weight over two to three weeks and adjust: if you are not moving in the direction you expected, your real TDEE is simply a little higher or lower than the formula guessed.
Why the formulas are only a starting point
Equations like Mifflin-St Jeor are population averages. Your real metabolism is shaped by muscle mass (muscle burns more at rest than fat), genetics, hormones, sleep, and even how much you fidget — a surprisingly large and individual factor researchers call NEAT, non-exercise activity thermogenesis. Two people with identical height, weight, age and sex can have BMRs that differ by a couple of hundred calories. Use the calculated number to start, then let the scale and the mirror fine-tune it.
You can compute both figures in seconds with our BMR calculator and Calorie / TDEE calculator, then sanity-check your weight category with the BMI calculator.