Calorie Calculator & Deficit Estimator
Calorie deficit calculator: maintenance calories by Mifflin-St Jeor, an intake target 500 kcal lower, and the weeks to your goal weight at that deficit. How it works
Use the Calorie Calculator & Deficit Estimator
About the Calorie Calculator & Deficit Estimator
The daily intake target is maintenance calories minus a daily deficit: 500 kcal unless you type another amount from 100 to 1,500. A man aged 30, 180 cm tall and 90 kg who trains 3 to 5 days a week has a Mifflin-St Jeor BMR of 1880 kcal, maintenance of 2914 kcal and a target of 2414 kcal, and getting to 80 kg takes about 22 weeks at that deficit. At a 1,000 kcal deficit his target is 1914 kcal and the time about 11 weeks.
Maintenance and target by activity level
| Activity level | Factor | Man, 30, 180 cm, 90 kg: maintenance | Man: target | Woman, 30, 165 cm, 70 kg: maintenance | Woman: target |
|---|---|---|---|---|---|
| Sedentary | 1.2 | 2256 kcal | 1756 kcal | 1704 kcal | 1204 kcal |
| Lightly active | 1.375 | 2585 kcal | 2085 kcal | 1953 kcal | 1453 kcal |
| Moderately active | 1.55 | 2914 kcal | 2414 kcal | 2201 kcal | 1701 kcal |
| Very active | 1.725 | 3243 kcal | 2743 kcal | 2450 kcal | 1950 kcal |
| Super active | 1.9 | 3572 kcal | 3072 kcal | 2698 kcal | 2198 kcal |
Maintenance is Mifflin-St Jeor BMR (1880 kcal for the man, 1420 kcal for the woman) times the factor. The target is maintenance minus the default 500 kcal deficit. Both are rounded to whole kcal.
Weeks to a goal weight at a 500 kcal deficit
| Weight to lose | Deficit to cover at 7,700 kcal per kg | Weeks shown |
|---|---|---|
| 2 kg | 15,400 kcal | 4 weeks |
| 5 kg | 38,500 kcal | 11 weeks |
| 10 kg | 77,000 kcal | 22 weeks |
| 15 kg | 115,500 kcal | 33 weeks |
| 20 kg | 154,000 kcal | 44 weeks |
| 30 kg | 231,000 kcal | 66 weeks |
Weeks are the deficit divided by 500 kcal a day, divided by 7 and rounded to a whole week. The figure does not depend on age, height or activity.
Losing 10 kg at different daily deficits
| Daily deficit | Target (man, 30, 180 cm, 90 kg, moderately active) | Days | Weeks shown |
|---|---|---|---|
| 250 kcal | 2664 kcal | 308 | 44 weeks |
| 500 kcal (default) | 2414 kcal | 154 | 22 weeks |
| 750 kcal | 2164 kcal | 103 | 15 weeks |
| 1,000 kcal | 1914 kcal | 77 | 11 weeks |
| 1,500 kcal | 1414 kcal, below the 1,500 kcal minimum for men (warning shown) | 51 | 7 weeks |
Maintenance is 2914 kcal in every row. Days = 77,000 kcal ÷ the daily deficit, rounded here to a whole day; weeks = days ÷ 7, rounded. The field accepts 100 to 1,500 kcal.
Methodology
Mifflin-St Jeor resting energy: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5 for men, or − 161 for women. Maintenance = BMR × an activity factor of 1.2, 1.375, 1.55, 1.725 or 1.9. The target is maintenance − the daily deficit, 500 kcal unless you enter another amount from 100 to 1,500. Weeks to the goal = (current kg − goal kg) × 7,700 ÷ daily deficit ÷ 7, rounded to a whole week, and the goal date is today plus the unrounded number of days. A target below 1,200 kcal (women) or 1,500 kcal (men) shows a warning.
How to use this tool
- Choose female or male and enter your age (19 to 78), height in centimeters, current weight in kilograms and goal weight in kilograms. There are no pound or inch fields: divide pounds by 2.2046 and multiply inches by 2.54.
- Pick the activity level that matches a normal week. Sedentary is the default.
- Leave the daily deficit at 500 kcal or type another amount from 100 to 1,500.
- Read maintenance calories, the daily intake target, the weeks to the goal and the goal date.
Frequently asked questions
- How do I calculate a calorie deficit?
- Estimate the calories you use in a day (maintenance), then subtract the amount you want to eat below it. This calculator estimates maintenance with the Mifflin-St Jeor equation times an activity factor and subtracts the daily deficit you set, 500 kcal by default. For the man in the example that is 2914 − 500 = 2414 kcal a day.
- How many calories should I eat to lose weight?
- This calculator’s answer is maintenance minus 500: 2414 kcal for the man in the example and 1701 kcal for a 30-year-old woman who is 165 cm, 70 kg and moderately active. Whether that suits you is a decision for you and a doctor or dietitian. Harvard Health says intake should not fall below 1,200 kcal a day for women or 1,500 for men except under the supervision of a health professional, and the page warns when the target is below those figures.
- How long will it take to lose 10 kg at a 500 calorie deficit?
- About 22 weeks, or 154 days. The calculator uses 7,700 kcal per kilogram, so 10 kg is 77,000 kcal, and 77,000 ÷ 500 = 154 days. At a 1,000 kcal deficit it is 77 days, or 11 weeks. The calculator holds the deficit and maintenance fixed for the whole period and does not adjust as your weight changes.
- How much weight is a 500 calorie deficit a week?
- A 500 kcal deficit is 3,500 kcal a week, which at 7,700 kcal per kilogram is about 0.45 kg, or 1.0 lb. Harvard Health puts a daily deficit of 500 to 1,000 calories at about 1 to 2 pounds of weight loss a week.
- Which equation does this calorie calculator use, and for what ages?
- Mifflin-St Jeor, from a 1990 study that measured resting energy in 498 adults aged 19 to 78. The calculator accepts only ages 19 to 78 and refuses a height and weight that give a BMI outside 12 to 60.
- What if my goal weight is higher than my current weight?
- The page shows maintenance calories only. There is no intake target and no weeks or goal date, because the deficit applies to losing weight.
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