How TDEE is estimated
Your total daily energy expenditure (TDEE) has two parts. Basal metabolic rate (BMR) is what your body burns at complete rest to keep you alive: breathing, circulation, temperature. Everything else, from digestion to walking to the shops to a gym session, is added with an activity multiplier.
The three BMR equations
Mifflin–St Jeor (1990) is the default. It was developed from measurements of 498 healthy adults, and a 2005 systematic review for the American Dietetic Association found it the most reliable of the common equations for people of normal weight and with obesity.
Women: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161
Revised Harris–Benedict (Roza and Shizgal, 1984) updates the original 1919 equation. It tends to give slightly higher numbers than Mifflin–St Jeor.
Women: 447.593 + 9.247 × kg + 3.098 × cm − 4.330 × age
Katch–McArdle uses lean body mass instead of total weight, so it does not need your sex or age. It can suit lean, muscular people, but only if your body fat percentage is reasonably accurate; bathroom scales can be off by several points.
To see only your resting burn from all three equations side by side, in kcal and kJ, use the BMR calculator.
Worked example
A 30-year-old man, 180 cm tall, weighing 80 kg, who exercises 3–5 days a week:
- BMR (Mifflin–St Jeor) = 10 × 80 + 6.25 × 180 − 5 × 30 + 5 = 800 + 1,125 − 150 + 5 = 1,780 kcal.
- Moderately active factor = 1.55, so TDEE = 1,780 × 1.55 = 2,759 kcal a day.
- To lose about 0.5 kg a week, eat roughly 550 kcal less: about 2,210 kcal a day.
Choosing an activity level
| 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 plus hard training |
These multipliers are widely used conventions rather than measurements. For comparison, the FAO/WHO/UNU expert report on human energy requirements describes sedentary or light lifestyles as about 1.40–1.69 times BMR, active lifestyles as 1.70–1.99 and vigorous ones as 2.00–2.40. If you are unsure, pick the lower level: overestimating activity is the most common reason a plan does not work.
Calories for your goal
The goal table uses the rough figure of 7,700 kcal per kilogram of body weight (about 3,500 kcal per pound), so a 0.5 kg weekly loss needs a deficit of about 550 kcal a day. Treat it as a starting point. Your TDEE drops as you lose weight, so progress slows unless you adjust; the calorie deficit calculator builds that into a dated plan.
Targets below about 1,200 kcal a day for women or 1,500 kcal for men are flagged, because going lower without medical supervision makes it hard to get enough nutrients.
Macro split
Calories come from carbohydrate and protein (4 kcal per gram) and fat (9 kcal per gram). The two suggested splits stay inside the Acceptable Macronutrient Distribution Ranges set by the US National Academies: 45–65% of calories from carbohydrate, 10–35% from protein and 20–35% from fat. The higher-protein option can help you feel full while losing weight. People with kidney disease, diabetes or other conditions should follow their own clinician’s advice.
Accuracy
Any equation is an average. Individual BMRs commonly differ from the prediction by 10% or more. Use your result for two to three weeks, track your weight, and adjust by 100–200 kcal a day if it moves faster or slower than planned. To see where your weight sits now, use the BMI calculator. For safe deficits and realistic rates of weight loss, read how many calories to eat to lose weight.