Calorie Deficit Calculator
This calorie deficit calculator works out your daily calorie target to reach a goal weight in a chosen number of weeks, based on your TDEE and roughly 7,700 kcal per kilogram of body fat, and warns you if the plan is too aggressive.
About this tool
This calorie deficit calculator works out your daily calorie target to reach a goal weight in a chosen number of weeks, based on your TDEE and roughly 7,700 kcal per kilogram of body fat, and warns you if the plan is too aggressive.
How to use it
- Enter your sex, age and height in cm.
- Enter your current weight, goal weight and timeframe in weeks.
- Choose your activity level.
- Read your TDEE, required daily deficit, daily calorie target and expected weekly loss.
Good to know
- TDEE is calculated with the Mifflin-St Jeor BMR equation multiplied by an activity factor.
- The plan assumes about 7,700 kcal per kilogram of body fat: daily deficit = (weight to lose × 7,700) ÷ days.
- Deficits above 1,000 kcal per day are flagged as too aggressive.
- Targets below 1,500 kcal per day for men or 1,200 kcal per day for women are flagged, as eating less than that is generally not recommended without medical supervision.
Runs entirely in your browser — nothing you enter is uploaded or stored.
Frequently asked questions
How big should my calorie deficit be?
A deficit of about 300–500 kcal per day is sustainable for most people and leads to roughly 0.25–0.5 kg of loss per week. Larger deficits make it harder to keep muscle, energy and adherence.
How fast can I safely lose weight?
A common guideline is 0.5–1% of body weight per week. If this calculator shows a deficit above 1,000 kcal a day, extend the timeframe.
Why am I not losing weight in a calorie deficit?
Water retention can hide fat loss for a week or two, and it is easy to underestimate intake or overestimate activity. Compare weekly averages over several weeks before adjusting.
Is it safe to eat 1,200 calories a day?
For many adults that is too low to cover nutritional needs, and it is shown here as a minimum rather than a target. Talk to a doctor or dietitian before following a very low-calorie diet.