Helpful Toolbox

Calorie Deficit Calculator

Find out exactly how many calories to eat per day to hit your weight-loss goal. Enter your maintenance calories (TDEE) — or let the tool estimate them from your stats — pick a weekly loss rate, and see your daily target and deficit instantly. Everything runs in your browser; nothing is uploaded.

📖 How it works & FAQ

How a calorie deficit turns into weight loss

Weight loss comes down to a simple gap: eating fewer calories than your body burns. Your total daily energy expenditure (TDEE) is everything you burn in a day — your basal metabolic rate (BMR) plus movement and exercise. This calculator uses the widely cited estimate of about 3,500 calories per pound of body fat, so a goal of 1 lb per week works out to 3,500 ÷ 7 = 500 calories below maintenance each day. Both the calories-per-pound figure and the activity multiplier are editable, so you can adjust them if you follow a different model.

If you don't know your TDEE, the tool estimates it with the Mifflin-St Jeor equation — one of the most accurate general-purpose BMR formulas — then multiplies by an activity factor from 1.2 (sedentary) to 1.9 (extremely active). All results are estimates only, not medical advice; individual metabolism varies, so check with a doctor or registered dietitian before making big changes.

How to use it

  1. Choose whether to enter your maintenance calories directly or estimate them from body stats.
  2. If estimating, fill in sex, age, weight, and height, then pick an activity level (fine-tune the multiplier if you like).
  3. Set your target weight loss in pounds per week — 0.5 to 2 lb is the commonly recommended range.
  4. Read your daily calorie target, daily deficit, and weekly deficit. The results update live as you type.

FAQ

Is a bigger deficit always better?
No. Very large deficits can cost you muscle, energy, and adherence. Most guidance favors 0.5–2 lb per week, and the tool warns you when you go past that or drop below roughly 1,200 calories (women) or 1,500 (men) per day.
Is the 3,500-calorie rule exact?
It's a useful approximation, not a law. Real-world loss slows over time as your body adapts and your maintenance drops. You can edit the calories-per-pound value to model other assumptions.
Should I include exercise calories?
Yes — through the activity multiplier. Pick the level that matches an average week rather than adding workouts on top, or you'll double-count them.
Is my data stored anywhere?
No. Everything is calculated in your browser; nothing is sent to a server.