Calorie Deficit Calculator: How Many Calories to Eat to Lose Weight
Find the daily calorie deficit you need to reach your goal weight by a target date. The calculator estimates your maintenance calories with the Mifflin-St Jeor equation, then turns your goal into a daily calorie target and flags plans that are too aggressive. Example: a 35-year-old man at 200 lb who wants to reach 180 lb in 20 weeks needs about a 500 calorie deficit per day.
Inches if US, centimeters if metric.
Pounds if US, kilograms if metric.
Show steps
How to use the Calorie Deficit Calculator
- Pick your units, sex and age, then enter your height and current weight.
- Enter your goal weight and the number of weeks you want to take.
- Choose the activity level that best matches a normal week.
- Press Calculate to see your daily calorie target, the deficit required, and how long other deficit sizes would take.
Formula and method
Maintenance calories come from the Mifflin-St Jeor equation: BMR = 10 × kg + 6.25 × cm − 5 × age + 5 (men) or − 161 (women), multiplied by an activity factor from 1.2 to 1.9.
One pound of body fat is about 3,500 kcal (7,700 kcal per kg), so daily deficit = pounds to lose × 3,500 / days. Example: 20 lb in 140 days = 70,000 / 140 = 500 kcal per day.
Frequently asked questions
How big should my calorie deficit be?
A deficit of 300 to 500 kcal a day is a common starting point, which is roughly 0.6 to 1 lb per week. Larger deficits can work short term but are harder to sustain and can cost muscle.
Is the 3,500 calorie rule accurate?
It is a useful estimate, not an exact law. Metabolism adapts as you lose weight, so progress usually slows over time. Re-run the calculator with your new weight every few weeks.
What is the minimum calorie intake?
Many guidelines suggest not going below about 1,200 kcal a day for women or 1,500 for men without medical supervision. Your needs may be higher.
Is this medical advice?
No. It is an educational estimate. Check with a doctor or registered dietitian before starting a diet, especially if you have a medical condition, are pregnant, or are under 18.
Sources
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