How big should a calorie deficit be?

For most people 250-500 calories a day is sustainable. Deficits above about 1% of body weight per week increase the loss of lean tissue and are harder to maintain.

Is a 1,000-calorie deficit too much?

It can be appropriate for a short period in people with a lot of weight to lose, but it often pushes intake below the point where nutrient needs are met. Check the flagged floor in the result.

How long until I see results on the scale?

Usually two to three weeks. Day-to-day scale movement is dominated by water and food volume, so use a weekly average.

Do I still need protein in a deficit?

Yes. Higher protein intake, roughly 1.8-2.4 g per kg, helps preserve lean mass while losing weight.

Calorie Deficit Calculator

Find the daily intake that creates the deficit you need for a target rate of weight loss.

Enter your details and your result will appear here.

What Is Calorie Deficit?

A calorie deficit means eating less energy than you use, which is the requirement for losing body weight. This calculator estimates your maintenance level, subtracts the deficit that matches the rate of loss you choose, and shows the intake to aim for.

Understanding Your Calorie Deficit Result

Rate of loss and size of deficit are the same decision. A 250-calorie daily deficit corresponds to about 0.5 lb a week, 500 calories to about 1 lb, and 1,000 calories to about 2 lb. Larger deficits are harder to sustain, and above roughly 1% of body weight per week the share of weight lost as lean tissue tends to rise.

How Is Calorie Deficit Calculated?

Target intake = TDEE - (weekly loss in lb x 3,500 / 7)

Methodology

Maintenance is estimated with Mifflin-St Jeor plus an activity factor. The chosen weekly rate is converted using the standard 3,500 calories per pound approximation and subtracted. If you enter a goal weight, the timeline divides the weight to lose by the weekly rate.

Worked Example

A 28-year-old man who is 6 ft 0 in and 210 lb, moderately active, has a maintenance of about 2,982 calories. Targeting 1 lb per week gives a 500-calorie deficit and an intake of about 2,482 calories. To reach 190 lb, the timeline is 20 weeks at that rate.

Important Limitations

Weight loss is not linear. As body mass falls, maintenance falls with it, so a fixed deficit shrinks in relative terms and progress slows. Water retention, glycogen and digestive contents can hide two weeks of real fat loss. This tool does not account for medical conditions or medications that affect weight.

Frequently Asked Questions

How big should a calorie deficit be?: For most people 250-500 calories a day is sustainable. Deficits above about 1% of body weight per week increase the loss of lean tissue and are harder to maintain.
Is a 1,000-calorie deficit too much?: It can be appropriate for a short period in people with a lot of weight to lose, but it often pushes intake below the point where nutrient needs are met. Check the flagged floor in the result.
How long until I see results on the scale?: Usually two to three weeks. Day-to-day scale movement is dominated by water and food volume, so use a weekly average.
Do I still need protein in a deficit?: Yes. Higher protein intake, roughly 1.8-2.4 g per kg, helps preserve lean mass while losing weight.