Calorie Deficit Calculator
Have a goal weight and a date in mind? See the daily calorie deficit it takes, what to eat, and whether the pace is realistic.
Your details
Your results
Enter your height, maintenance calories, current and goal weight, and deadline.
Daily deficit needed
kcal a day
The model estimates kcal a day for a starting pace of a week ( of your bodyweight).
How to use it
- Enter your maintenance calories. Don't know them? Get them from the TDEE Calculator first.
- Enter your height, current weight, goal weight and the number of weeks you have.
- Read the estimated deficit and intake. If a longer timeline fits the calculator’s limits, the calculator will suggest one.
How it's calculated
The deficit. A kilogram of body weight holds about 7,700 kcal (the “3,500 kcal per pound” rule; Hall, 2008):
daily deficit = (current weight − goal weight) × 7,700 ÷ (weeks × 7)
Your daily target is your maintenance calories minus that deficit, rounded to the nearest 10 kcal. Pounds are converted to kilograms first.
Example: going from 85 to 80 kg in 10 weeks needs 5 × 7,700 ÷ 70 = 550 kcal a day. With maintenance at 2,500 kcal, that’s about 1,950 kcal a day.
Plan limits. The calculator withholds targets for goals below adult BMI 18.5, intakes below 1,250 kcal/day, deficits above 1,000 kcal/day or starting losses above 1% of bodyweight per week. The intake cutoff is a site limit above the range NICE reserves for supervised low-energy diets. A suggested deadline accounts for the intake, deficit and weekly pace limits together.
Limits. The 7,700 kcal rule assumes your maintenance stays the same. In reality it drops as you lose weight, so a fixed deficit loses less over time. For long plans, the Weight Loss Timeline Calculator models that.
Sources
- Hall, K. D. (2008). What is the required energy deficit per unit weight loss? International Journal of Obesity, 32(3), 573–576.
- National Heart, Lung, and Blood Institute (1998). Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults. NIH Publication No. 98-4083.
- Helms, E. R., Aragon, A. A., & Fitschen, P. J. (2014). Evidence-based recommendations for natural bodybuilding contest preparation: nutrition and supplementation. Journal of the International Society of Sports Nutrition, 11, 20.
- NICE. Overweight and obesity management (NG246). Low-energy and very-low-energy diets for adults.
- World Health Organization (2000). Obesity: preventing and managing the global epidemic. Technical Report Series 894. Adult BMI classification.
Questions
What's a good calorie deficit?
US guidelines (NHLBI) suggest 500 to 1,000 kcal a day, which works out to about 0.5 to 1 kg (1 to 2 lb) a week. If you lift and want to keep your muscle, losing 0.5 to 1% of your bodyweight a week is a good pace.
Why does it suggest more weeks?
The calculator checks the deficit, weekly pace and daily intake together. It suggests a longer timeline only if one fits all three limits.
How is this different from the Calorie Calculator?
The Calorie Calculator starts from a rate you pick, like 0.5 kg a week. This one starts from a deadline and works backwards to the deficit you need.
Will I lose weight in a straight line?
No. Water and food in your gut make daily weight jump around, and loss slows down as you get lighter. Watch your weekly average, and see the Weight Loss Timeline Calculator for how the pace changes.
Updated November 9, 2026.