Find out exactly how many calories your body needs each day
Enter your age, height, weight, sex, and activity level above, and this calorie calculator gives you three numbers: your BMR (the calories your body burns just staying alive), your TDEE (total daily calories burned with your lifestyle factored in), and adjusted targets for losing or gaining weight.
Everything runs in your browser. No data is sent to any server, so your personal details stay completely private.
How to use this calorie calculator
- Age – type your age in years.
- Sex – select male or female (the formula uses different constants for each).
- Height – enter in centimetres (e.g. 175 cm).
- Weight – enter in kilograms (e.g. 72 kg).
- Activity level – pick the option that best matches your typical week (see the table below).
- Hit Calculate and read your BMR, TDEE, and the calorie targets for losing or gaining ~0.5 kg per week.
Worked example
Imagine a 34-year-old woman, 163 cm tall, weighing 68 kg, who works a desk job and walks lightly a few times a week (lightly active).
- BMR: ~1,441 kcal/day
- TDEE (lightly active): ~1,441 × 1.375 ≈ 1,981 kcal/day to maintain weight
- To lose ~0.5 kg/week: ~1,481 kcal/day (a 500 kcal deficit)
- To gain ~0.5 kg/week: ~2,481 kcal/day (a 500 kcal surplus)
Those numbers give her a concrete starting point to track against — not a rigid rule, but a useful guide.
How your calorie needs are calculated (the formula)
This tool uses the Mifflin-St Jeor equation, published in 1990 and consistently rated as one of the most accurate BMR formulas for most adults by nutrition researchers.
Step 1 – BMR (Basal Metabolic Rate)
BMR is the number of calories your body burns at complete rest — breathing, pumping blood, keeping your organs running.
For men: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) + 5
For women: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) − 161Step 2 – TDEE (Total Daily Energy Expenditure)
TDEE is your BMR multiplied by an activity factor that accounts for how much you move each day. This gives you your true daily calorie burn.
| Activity level | What it looks like | Multiplier |
|---|---|---|
| Sedentary | Desk job, little or no exercise | × 1.2 |
| Lightly active | Light exercise 1–3 days/week | × 1.375 |
| Moderately active | Moderate exercise 3–5 days/week | × 1.55 |
| Active | Hard exercise 6–7 days/week | × 1.725 |
| Very active | Physical job + hard daily training | × 1.9 |
Using the worked example above: TDEE = 1,441 × 1.375 ≈ 1,981 kcal/day. That is how many calories she needs to eat to stay exactly the same weight.
Step 3 – Adjusting for weight change
One kilogram of body fat holds roughly 7,700 kcal of energy. Cutting or adding ~500 kcal per day creates a deficit or surplus of ~3,500 kcal per week — enough to change weight by about 0.5 kg per week. That pace is widely considered safe and sustainable.
How to read your result — and its limits
The number you get is an estimate, not a lab measurement. Real metabolic rates vary by up to 15–20% between people of the same age, height, and weight, because of differences in muscle mass, hormones, gut bacteria, and genetics.
Treat your TDEE as a starting point. Track your actual weight over two to four weeks. If it does not change as expected, adjust your intake by 100–200 kcal and re-check.
Also note that the formula does not distinguish muscle from fat. Someone who strength-trains and carries a lot of lean muscle may burn significantly more than the formula predicts.
Practical tips for reaching your goal
- Prioritise protein. Aim for roughly 1.6–2.2 g per kg of body weight daily. Protein keeps you fuller and helps preserve muscle when you are in a calorie deficit.
- Move more in small ways. Standing, walking to meetings, taking stairs — these lifestyle calories (called NEAT) can add up to several hundred kilocalories a day without any formal exercise.
- Don't cut too sharply. Deficits larger than 1,000 kcal/day often lead to muscle loss, fatigue, and rebound overeating. Slow, steady progress tends to stick.
- Sleep matters. Poor sleep raises hunger hormones (ghrelin) and reduces fullness hormones (leptin), making it harder to stay within your calorie target.
- Track what you eat for a week. Most people underestimate portions by 20–40%. Even a rough food diary closes that gap quickly.
- Stay hydrated. Thirst is sometimes mistaken for hunger. Drinking water before meals can reduce unnecessary snacking.
A note on accuracy and medical advice
This tool is for general education only — it is not medical advice. Calorie needs are influenced by health conditions, medications, pregnancy, and other factors this calculator cannot know about. If you are managing a medical condition, pregnant, or have a history of disordered eating, please speak with a doctor or registered dietitian before changing your diet.
For reliable general guidance on healthy eating and energy balance, the WHO healthy diet fact sheet and the NHS guide to understanding calories are both trustworthy, free resources.
Your next step: plug your numbers into the calculator above and use your TDEE as the anchor for your daily calorie target — then adjust based on real results over the following few weeks.