This weight loss calculator shows how many calories to eat and when you could reach your goal weight. Unlike simple “3,500 calories per pound” tools, it recalculates your calorie needs as your weight falls, so the goal date is more realistic.
How the goal date is worked out
- Your resting energy use (BMR) is estimated with the Mifflin-St Jeor equation from your sex, age, height and weight.
- It is multiplied by your activity level to give your total daily energy expenditure (TDEE).
- Your daily calories = TDEE − your chosen deficit.
- Each day, the calculator subtracts the energy gap (about 7,700 kcal per kg, or 3,500 kcal per pound, of body fat) and recalculates your TDEE at the new weight.
Because a lighter body burns fewer calories, weight loss naturally slows over time at the same intake.
Worked example
A 35-year-old woman, 5 ft 6 in and 190 lb, who is lightly active burns about 2,164 calories a day. Eating 1,664 calories (a 500-calorie deficit), she could reach 160 lb in about 38 weeks.
How fast should I lose weight?
Health services in the US, UK and Australia commonly suggest about 0.5 to 1 kg (1 to 2 lb) a week. Faster loss is harder to keep up and more likely to include muscle. Very low-calorie diets should only be followed with medical supervision.
Frequently asked questions
How many calories should I eat to lose weight?
Most people lose about 1 lb (0.5 kg) a week by eating 500 calories less than they burn. The calculator works out your personal number.
Why does my weight loss slow down?
As you lose weight, your body needs fewer calories, so the same intake creates a smaller deficit. Water weight early on also makes the first weeks look faster.
Is 1,200 calories a day safe?
For many women it is a common lower limit, and about 1,500 for men. Eating less than that makes it hard to get enough nutrients without medical supervision.
Should I exercise as well?
Yes. Exercise increases calories burned and helps keep muscle, which makes it easier to maintain your new weight.
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Sources
Last reviewed: October 2026. For information only; not medical advice. Talk to a doctor about any health concerns.