Calorie Deficit Calculator
Example: Pounds you want to lose: 20 lb · Timeframe: 16 weeks
| Daily calorie deficit needed | 625 |
| Weekly calorie deficit | 4,375 |
| Weekly loss rate | 1.25 |
Worked example
Suppose you want to lose 20 lb over 16 weeks. That is 20 x 3,500 = 70,000 total calories to shed, or 70,000 / 16 = 4,375 calories per week. Divide by 7 and you need a daily deficit of about 625 calories, which produces roughly 1.25 lb of loss per week. That pace sits comfortably inside the safe 1-to-2-pound-per-week range health authorities recommend.
Frequently asked questions
How big a daily deficit is safe?
Most health authorities suggest aiming for 1 to 2 pounds of loss per week, which is a deficit of roughly 500 to 1,000 calories a day. Much larger deficits can cost you muscle, energy, and adherence. If this tool returns a deficit above about 1,000, consider extending your timeframe.
Is the 3,500-calories-per-pound rule exact?
It is a useful approximation, not a law of physics. Real weight loss slows as you get lighter and your metabolism adapts, so treat the number as a starting target and adjust based on the scale over a few weeks rather than expecting it to be perfect.
Should I create the deficit through diet or exercise?
A mix usually works best. Diet is the more powerful lever for the deficit itself because it is easy to eat back the calories a workout burns, while exercise protects muscle, improves fitness, and supports appetite control. Combining both is more sustainable than relying on either alone.
Why is my real-world loss slower than the estimate?
Water retention, glycogen shifts, sodium, and hormones make the scale bounce day to day, and metabolic adaptation reduces your burn as you lose. Judge progress over 2 to 4 weeks, and re-run the calculator with your updated weight to keep the target honest.