Calculate Your Calories
BMR, TDEE and Your Exact Daily Numbers
No app, no guesswork, no generic plan. Two calculations and a handful of numbers give you a precise daily calorie target — built around your actual body, your actual activity level, and your actual goal.
These calculations are evidence-based starting points for healthy adults. They are not personalised medical or dietary advice. If you have a medical condition — including Type 1 or Type 2 diabetes, kidney disease or cardiovascular disease — please speak to your GP or a registered dietitian before making significant changes to your diet or calorie intake.
What Is a Calorie?
A calorie is a unit of energy. Specifically, it is the amount of energy required to raise the temperature of one gram of water by one degree Celsius. In nutritional terms, the calories listed on food packaging are kilocalories — one thousand of those units — though the word calorie is used for both in everyday language.
Your body uses calories to do everything: breathe, pump blood, repair tissue, move, think. The number of calories you consume versus the number you expend determines whether you gain weight, lose weight or stay the same. This is thermodynamics — not theory.
The Three Numbers to Remember
Every macro calculation in the world is built on three fixed values. Memorise these and you can work out the calorie content of any food from a label — without an app.
Basal Metabolic Rate — Your Baseline
BMR is the number of calories your body burns at complete rest — simply to keep you alive. Heart beating, lungs working, cells repairing. If you stayed in bed for 24 hours and did absolutely nothing, you would still burn this many calories.
It is calculated using the Harris-Benedict equation — one of the most widely used and well-researched formulas in sports nutrition, originally developed in 1919 and revised for greater accuracy in 1984. You need four pieces of information: weight in kilograms, height in centimetres, age in years, and sex. That is all.
Total Daily Energy Expenditure
BMR tells you how many calories you burn at rest. TDEE accounts for everything you actually do across a full day. Multiply your BMR by the activity factor that best reflects your week. Your TDEE is your maintenance number — eat below it to lose weight, above it to gain.
| Activity Level | Description | Multiplier |
|---|---|---|
| Sedentary | Little or no exercise | BMR × 1.2 |
| Lightly active | Light exercise 1–3 days per week | BMR × 1.375 |
| Moderately active | Moderate exercise 3–5 days per week | BMR × 1.55 |
| Very active | Hard exercise 6–7 days per week | BMR × 1.725 |
| Extremely active | Hard daily exercise plus a physically demanding job | BMR × 1.9 |
Three Worked Examples
The following examples use real numbers. All three assume a moderately active male training three to five times per week. The variables that change are age, height, weight and goal.
89kg · 40 years old · 175cm · Wants to lose 10kg
Fat at 25%: 2,435 × 0.25 = 609 kcal ÷ 9 = 68g fat
Carbohydrates: (2,435 − 640 − 609) ÷ 4 = 296g carbohydrates
75kg · 52 years old · 178cm · Wants to build muscle
Fat at 30%: 2,983 × 0.30 = 895 kcal ÷ 9 = 99g fat
Carbohydrates: (2,983 − 600 − 895) ÷ 4 = 372g carbohydrates
95kg · 45 years old · 182cm · Wants to maintain weight and improve body composition
Fat at 25%: 3,116 × 0.25 = 779 kcal ÷ 9 = 87g fat
Carbohydrates: (3,116 − 760 − 779) ÷ 4 = 394g carbohydrates
These are starting points, not prescriptions. The calculations provide a solid evidence-based starting point. Real results come from testing, tracking and adjusting over 4–6 weeks based on what your body actually does. If weight is not changing in the expected direction after two weeks, adjust calories by 100–200 per day and reassess.
Related Topics
References
Harris JA, Benedict FG. A Biometric Study of Basal Metabolism in Man. Carnegie Institution of Washington, 1919. Revised by Roza AM, Shizgal HM. American Journal of Clinical Nutrition, 1984; 40(1): 168–182.
The 1984 Roza-Shizgal revision produced the coefficients used in the formulas on this page and remains the most widely applied version in clinical and sports nutrition practice.
Atwater WO, Benedict FG. Experiments on the Metabolism of Matter and Energy in the Human Body. US Department of Agriculture, 1902. Codified in FAO Food and Nutrition Paper 77, Rome, 2003.
4 kcal/g protein, 4 kcal/g carbohydrate, 9 kcal/g fat — the universal standard for food labelling and nutrition science worldwide.
Aragon AA, Tipton KD, Schoenfeld BJ. Age-related muscle anabolic resistance: inevitable or preventable? Nutrition Reviews, 2023; 81(4): 441–454.
The basis for the higher protein targets (2.0g/kg) used in the over-50 worked examples. Older adults require greater protein intake to achieve the same muscle protein synthetic response as younger individuals.
