Calorie Deficit Calculator

Choose a daily calorie deficit and see your daily calorie target, how much you could lose each week and roughly when you'd reach your goal weight.

Units
Sex
Estimated goal date
–
Daily calorie target–
Maintenance calories–
Weight to lose–
Time needed–

How the calculation works

Maintenance = BMR (Mifflin-St Jeor) × activity factor
Daily target = maintenance − daily deficit
Days to goal = pounds to lose × 3,500 ÷ daily deficit

The 3,500-calories-per-pound figure is a rule of thumb. As you lose weight your maintenance calories also fall, so if you keep eating the same amount your deficit gets smaller. That is why real-world progress often slows, and why it helps to recalculate every 5 to 10 lb.

Worked example

Someone who maintains on 2,300 calories a day, weighs 170 lb and wants to reach 155 lb picks a 500-calorie deficit. Their target is 1,800 calories a day. Losing 15 lb × 3,500 = 52,500 calories, divided by 500 a day, is 105 days, or about 15 weeks.

Making a deficit easier to keep

  • Eat enough protein and fiber to stay full. The protein calculator gives a daily range.
  • Add movement you enjoy, such as walking. Track it with the steps to miles calculator.
  • Plan for weekends and social meals instead of aiming for perfection.
  • Weigh yourself at the same time of day and look at the weekly trend, not single days.

To see your full calorie needs by goal, use the calorie calculator. This tool is for general information and is not medical advice.

Last reviewed October 2026.

Frequently asked questions

What is a calorie deficit?

A calorie deficit means eating fewer calories than your body uses in a day. Your body makes up the difference from stored energy, which over time leads to weight loss. The bigger the gap, the faster the expected loss.

How long will it take to reach my goal weight?

This calculator divides the weight you want to lose by your daily deficit, using the common estimate of about 3,500 calories per pound (7,700 per kg). Real progress usually slows over time because a smaller body burns fewer calories, so treat the date as an optimistic estimate.

What deficit is reasonable?

A daily deficit of around 300 to 500 calories, about 0.5 to 1 lb a week, is a pace many people can keep up. Bigger deficits are harder to sustain. The calculator warns you when your target falls below commonly quoted minimums.

Does exercise count towards the deficit?

Yes. Your deficit is the difference between calories burned and calories eaten, so more activity raises your daily burn. Pick the activity level that matches your typical week rather than your best week.

Who should not use this?

It is meant for healthy adults. Do not use it if you are pregnant, breastfeeding, under 18, or have a medical condition or a history of disordered eating. Speak with a doctor or registered dietitian for personal advice.