Free calculator

Calorie deficit calculator

See how many calories to eat to lose weight at the pace you choose. You get a target for every weekly goal, the deficit as a share of your maintenance calories, and a goal date if you add a goal weight.

Enter your sex, age, height and weight plus activity level, weekly goal, goal weight. The calculator runs in your browser and nothing is stored.

The formula

Daily target = TDEE − (weekly goal in kg × 7,700 ÷ 7)

  • TDEE = Mifflin-St Jeor BMR × activity multiplier
  • 7,700 kcal is the approximate energy in 1 kg of body fat (about 3,500 kcal per lb)
  • 0.25 kg a week ≈ 275 kcal a day, 0.5 kg ≈ 550 kcal, 0.75 kg ≈ 825 kcal
  • The target never goes below 1,200 kcal a day

How the calorie deficit calculator works

It estimates your maintenance calories (TDEE) from your age, sex, height, weight and activity level. It then subtracts the daily deficit needed for your weekly goal. A kilogram of body fat holds roughly 7,700 kcal, so losing 0.5 kg a week takes a daily deficit of about 550 kcal. This is the same maths as the Low Cal app.

Choosing a pace

A sustainable deficit is usually 10–25% of your TDEE, or a loss of about 0.5–1% of your body weight a week. The table in your result shows each weekly goal as a percentage of your maintenance calories:

  • Under 15%: slow and easy to keep up. Good if you are already fairly lean or have a small TDEE.
  • 15–25%: the sweet spot for most people.
  • Over 25%: more hunger and fatigue, and a higher risk of losing muscle. Keep phases short.

If your target hits the 1,200 kcal floor, that pace isn't realistic for your body size. Choose a slower goal or add daily movement instead of cutting further.

Why the goal date is an estimate

The goal date assumes the pace stays constant. In reality, weight loss slows as your body gets smaller and adapts. NIH modelling shows that simple 7,700 kcal-per-kg projections overestimate long-term loss. Expect the last few kilograms to take longer, and recalculate your target after every 4–5 kg of loss.

Keep the weight you lose as fat

Losing fat rather than muscle depends mainly on two things: enough protein (at least about 1.6 g per kg of body weight during a diet; see the protein calculator) and strength training two to four times a week. The calorie deficit guide covers plateaus, diet breaks and water weight.

Check and adjust

After two to three weeks at your target, compare your average weekly weight change with the goal. Each 0.1 kg a week of difference is about 110 kcal a day. Adjust by 100–200 kcal at a time, not by crashing your intake.

Sources

Calorie deficit calculator questions

How big should my calorie deficit be?

For most people, 10–25% below maintenance, which is often 300–600 kcal a day. Bigger deficits cause more hunger and muscle loss and are harder to keep up.

Is 500 calories a day a good deficit?

For many adults, yes: it works out to roughly 0.45 kg (1 lb) a week at first. For smaller or less active people, 500 kcal can be more than 25% of maintenance, so a smaller deficit is easier to sustain.

Why is my target 1,200 calories?

The calculator does not go below 1,200 kcal a day, because below that it becomes hard to meet nutrient needs without medical supervision. If you hit the floor, choose a slower weekly goal.

Why am I not losing weight in a deficit?

Usually intake is higher than logged, activity is lower than the level chosen, or water retention is hiding fat loss. Check a three-week weight trend and a week of careful logging before cutting further.

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