How many calories you need each day depends on two things: the energy your body burns just staying alive, and how active you are on top of that. This calculator estimates both — your Basal Metabolic Rate (BMR) and your Total Daily Energy Expenditure (TDEE) — and then shows the calorie intake for maintaining, losing or gaining weight at a sensible pace.

How it works

Enter your age, sex, height and weight, then pick the activity level that best matches your typical week — be honest here, because this choice moves the result more than any other. The calculator first works out your BMR, the calories you would burn in a day of complete rest. It then multiplies that by an activity factor to get your TDEE: the number of calories that keeps your weight stable.

From your TDEE, the calculator suggests a target for gradual weight loss (TDEE minus 500 kcal) and for gradual gain (TDEE plus 500 kcal).

How the calculation works

The calculator uses the Mifflin-St Jeor equation, which studies have found to be the most accurate of the common BMR formulas:

• Men: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) + 5
• Women: BMR = (10 × weight in kg) + (6.25 × height in cm) − (5 × age) − 161

That BMR is then multiplied by an activity factor:

• 1.2 — sedentary (desk job, little exercise)
• 1.375 — lightly active (light exercise 1–3 days a week)
• 1.55 — moderately active (exercise 3–5 days a week)
• 1.725 — very active (hard exercise 6–7 days a week)
• 1.9 — athlete level (physical job plus daily training)

As a rule of thumb, a daily deficit or surplus of about 500 kcal produces a change of roughly 0.5 kg per week. For safety, intakes should not drop below about 1,200 kcal a day for women or 1,500 kcal a day for men without medical supervision — if your calculated target falls below those floors, aim for a slower rate of loss instead.

Worked example

A woman, age 34, 68 kg, 165 cm tall, with a moderately active lifestyle:

1. BMR: (10 × 68) + (6.25 × 165) − (5 × 34) − 161 = 680 + 1,031 − 170 − 161 = 1,380 kcal/day
2. TDEE: 1,380 × 1.55 = 2,139 kcal/day to maintain her weight
3. Weight-loss target: 2,139 − 500 = about 1,640 kcal/day, which should give a loss of roughly 0.5 kg a week

If she had picked “sedentary” (×1.2), her maintenance would be only about 1,656 kcal — barely above the loss target. That is why the activity choice matters so much, and why people with desk jobs often need to add activity, not just cut food, to lose weight comfortably.

Tips

• Most people overestimate their activity. If you train three times a week but sit at a desk for the other 160 hours, “lightly active” is probably closer to the truth than “moderately active”. Start with the lower estimate and adjust.
• Recalculate as you lose weight. A lighter body needs fewer calories. After every 5 kg lost, run the calculator again — otherwise your deficit quietly shrinks and your progress stalls.
• Give any target two to three weeks. Daily weight swings from water, salt and digestion can hide fat loss for days. Judge a calorie target by the trend over a fortnight, not by tomorrow’s weigh-in.
• Prioritise protein when cutting. Adequate protein (roughly 1.2–2 g per kg of body weight) helps preserve muscle and keeps hunger manageable on fewer calories.
• Count drinks and cooking oils. A latte, a glug of olive oil and a glass of wine can quietly add 400–500 kcal — often the entire intended deficit.

FAQ

What is the difference between BMR and TDEE?
BMR is the energy your body needs at complete rest for basic functions like breathing and circulation. TDEE is BMR plus everything you actually do — walking, working, exercising, even fidgeting. You eat to your TDEE, not your BMR.

How many calories do I need to lose 0.5 kg a week?
About 500 kcal per day below your TDEE, which adds up to roughly 3,500 kcal over the week. Keep your intake above 1,200 kcal (women) or 1,500 kcal (men) unless a clinician advises otherwise.

Why has my weight loss stalled on the same calories?
Usually because your TDEE has fallen: you weigh less, you may move slightly less, and your body adapts modestly. Recalculate with your new weight and be patient — genuine plateaus of a week or two are normal.

Are these figures exact for me personally?
No formula is. Mifflin-St Jeor lands within about 10% of measured BMR for most people, but individual variation exists. Treat the output as a starting point, then adjust by 100–200 kcal based on what your weight actually does over two or three weeks.

Do I need to eat back calories burned during exercise?
Not if you used an activity multiplier — exercise is already included in your TDEE. Adding exercise calories from a fitness tracker on top usually double-counts them and erases the deficit.

This calculator is for general information only and is not medical advice. Speak to your GP or a registered dietitian before starting a weight-loss plan, especially if you have a medical condition.