Results are estimates for healthy adults unless stated, and are not medical advice. Your doctor or a registered dietitian can give advice for your situation.
To lose weight you need to use more energy than you eat: a calorie deficit. This calculator estimates how many calories you burn, sets a daily target for the pace you choose, and shows roughly how long it will take to reach your goal, whether that is 5 kg, 10 lb or more.
How to use the calorie deficit calculator
- Enter your sex, age, height, weight and activity level.
- Enter how much weight you want to lose and pick a pace.
- Use the daily calorie target as a starting point and adjust based on your progress.
How it works
First, the calculator estimates your basal metabolic rate with the Mifflin-St Jeor equation, then multiplies it by your activity level to get your total daily energy expenditure (TDEE). It then subtracts a daily deficit based on the rule of thumb that losing 1 kg of body fat takes about 7,700 kcal (about 3,500 kcal per pound).
- 0.25 kg a week ≈ 275 kcal a day
- 0.5 kg a week ≈ 550 kcal a day
- 1 kg a week ≈ 1,100 kcal a day
The target is never set below 1,200 kcal for women or 1,500 kcal for men, common minimums for dieting without medical supervision.
Example: how long to lose 5 kg?
A 30-year-old woman who is 165 cm tall, weighs 75 kg and is lightly active burns roughly 2,020 kcal a day. At 0.5 kg a week she would eat about 1,470 kcal a day and reach a 5 kg loss in about 10 weeks.
Frequently asked questions
What is a safe rate of weight loss?
Most health services suggest about 0.5–1 kg (1–2 lb) a week. Slower loss is easier to keep up and helps protect muscle.
Why has my weight loss slowed down?
As you lose weight, you burn fewer calories, so the same intake creates a smaller deficit. Recalculate every 4–5 kg. Day-to-day changes in water and salt can also hide fat loss for a week or two.
Do I need to count calories forever?
No. Many people track for a few weeks to learn portion sizes, then switch to simpler habits like regular meals, more vegetables and protein, and fewer sugary drinks.
Sources
- Mifflin MD, St Jeor ST et al., American Journal of Clinical Nutrition (1990)
- National Institutes of Health (NIH) – Body Weight Planner research
- Centers for Disease Control and Prevention (CDC) – healthy weight loss
If you are pregnant, breastfeeding, under 18, have diabetes or have a history of eating disorders, speak to a doctor or registered dietitian before cutting calories.