Estimates only, based on the Mifflin-St Jeor equation. Not medical advice. Adults only.
About this tool
A calorie deficit means eating fewer calories than your body burns, which is how weight loss happens. This calculator estimates your daily calorie target, how fast you could lose weight at a chosen deficit, and roughly how many weeks it would take to reach your goal weight. It builds on your estimated TDEE, so you only enter your details once. It runs in your browser and nothing is stored.
How to use it
Enter your details and your goal weight, then pick a daily deficit. The result shows your target calories, the estimated weekly loss and the estimated time to reach your goal. A deficit of 250 to 500 calories is the usual range. If the target falls below the commonly cited minimum of 1,200 calories for women or 1,500 for men, the page flags it, and you should choose a smaller deficit. To see your maintenance level first, use the TDEE calculator.
How the numbers are worked out
Target calories = TDEE minus your daily deficit. Weekly loss is estimated from the rule of thumb that about 7,700 calories equals one kilogram (3,500 per pound). For example, a 500 calorie deficit each day is 3,500 a week, so about 0.45 kg (1 lb) a week. Weeks to goal = weight to lose divided by weekly loss. If you need to lose 10 kg at a 500 calorie deficit, that is roughly 22 weeks.
Choosing a deficit
- 250 calories: about 0.2 kg (0.5 lb) a week. Easy to sustain and keeps hunger low.
- 500 calories: about 0.45 kg (1 lb) a week. The most common recommendation.
- 750 calories: about 0.7 kg (1.5 lb) a week. Harder, and not suitable for everyone.
- 1,000 calories: about 0.9 kg (2 lb) a week. Usually too aggressive, and only for people with a lot to lose and medical guidance.
Important limits of any calorie calculator
These numbers are estimates. The equation is based on averages, and real needs differ by muscle mass, genetics, medications and health conditions. Use the result as a starting point, track your weight over two to three weeks, and adjust. Do not eat below the minimum shown without medical supervision, and speak to a doctor or registered dietitian before making big changes, especially if you are pregnant, breastfeeding, under 18, or managing a health condition. This tool is for adults.
Things to watch out for
The time estimate is only a guide. As you lose weight your TDEE drops, so the same deficit slows down, and real progress is rarely a straight line. Water weight can hide fat loss for days. Aim to lose weight gradually, keep enough protein, and consider getting advice from a doctor or dietitian. If you notice that you are becoming preoccupied with food or weight, speak to a health professional.
Frequently asked questions
A deficit of 250 to 500 calories a day is common and usually sustainable. Larger deficits are harder to maintain and are not suitable for everyone.
At a 500 calorie daily deficit, expect roughly 0.45 kg (1 lb) a week. Divide the weight you want to lose by that pace to estimate weeks, but remember progress slows over time.
1,200 calories (women) and 1,500 (men) are commonly cited minimums for unsupervised diets. Lower intakes should only be used under medical supervision.