Calorie deficit calculator

How many calories a day to reach your goal weight at a steady pace, how many weeks it takes, and the limits not to cross.

Calories a day to start

1,585 calories

11 weeks from 143 lb to 132 lb

499 below what you burn
1,508 by 132 lb
2,007 to stay at 132 lb

To go from 143 lb to 132 lb at 1 lb a week, you’d start at about 1,585 calories a day, 499 fewer than the 2,084 you burn now. You’d get there in about 11 weeks.

As you get lighter, you burn a little less, so keeping the pace means about 1,508 a day by the time you reach 132 lb. If you stay at 1,585 instead, it takes about 12 weeks.

I’m not a doctor or a dietitian. This is an estimate, for information only. For decisions about your health, check with a professional.

Your numbers

example: change the numbers

Units

The math stays the same. Only the way the numbers are shown changes.

Metrickg · cmUSlb · ftUKst · ft

Sex

The formula has one version for men and one for women.

FemaleMale

Age

For adults: the formula was built on people aged 19 to 78.

Height

Weight today

Goal weight

Lower than your weight today.

How active you are

Think of a typical week, including your job.

How fast

Pounds a week. The CDC calls 1 to 2 pounds a week a gradual, steady pace.

½ lb a weekabout 0.25 kg1 lb a weekabout 0.45 kg1½ lb a weekabout 0.7 kg2 lb a weekabout 0.9 kg

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Week by week
Week	At 1 lb a week	Calories a day	If you stay at 1,585
Start	143 lb	1,585	143 lb
1	142 lb	1,578	142 lb
2	141 lb	1,571	141 lb
3	140 lb	1,564	140 lb
4	139 lb	1,557	139 lb
5	138 lb	1,550	138 lb
6	137 lb	1,543	137 lb
7	136 lb	1,536	136 lb
8	135 lb	1,529	135 lb
9	134 lb	1,522	135 lb
10	133 lb	1,515	134 lb
11	132 lb	1,508	133 lb
12	—	—	132 lb

How it works

First, the calories you burn now, as in the calorie calculator: your resting burn with the Mifflin-St Jeor equation, times your activity level.
Then the deficit. Each kilogram lost is counted as 7,700 calories, which is 3,493 per pound: the metric form of the classic rule of 3,500 calories per pound. Divide by 7 to get a daily figure: 1 lb a week means about 499 fewer calories a day.
Weeks to your goal = pounds to lose ÷ pounds a week. A lighter body burns less, so to keep the pace the calories go down a little every week: the table shows them week by week, next to what happens if you keep eating the starting amount.

Worked example

A moderately active 35-year-old woman, 5 ft 5 in, going from 143 lb to 132 lb at 1 lb a week. Today she burns 2,084 calories a day. 1 lb a week is 0.4536 kg × 7,700 ÷ 7 = 499 calories a day, so she starts at 1,585. 11 lb ÷ 1 lb a week = 11 weeks. At 132 lb she burns about 2,007, so the pace needs 1,508 by the end. If she stays at 1,585 every day, it takes about 12 weeks.

Sources

Text checked on September 30, 2026

Good to know

The 3,500-calories-a-pound rule is a simplification. An NIH researcher found it fits people with more body fat; for leaner people, more of the weight lost is lean tissue, so each pound takes fewer calories but less of it is fat.
Your body adapts. In NIH modeling, weight responds slowly to a steady calorie intake, taking about a year to get halfway to where it settles. That’s why the plan lowers your calories week by week, and why the last column slows down.
The warnings use the limits in the sources: 1 to 2 pounds a week (CDC), the 1,200 (women) and 1,500 (men) calories a day at the bottom of the US guidelines’ usual diet plans, and 800 calories, below which diets are done only under a doctor’s supervision.
The plan is a straight line; real weigh-ins won’t be. For a model that also accounts for how your metabolism adapts, try the NIH’s Body Weight Planner.
If you’re pregnant or breastfeeding, have a health condition or take medication, talk to your doctor before cutting calories.

Frequently asked questions

How big a calorie deficit is safe?

The CDC calls about 1 to 2 pounds a week a gradual, steady pace that’s easier to keep off; the NHS says 0.5 to 1 kg (1 to 2 lb) a week. US obesity guidelines usually mean 500 to 750 fewer calories a day, with women at 1,200 to 1,500 a day and men at 1,500 to 1,800. Your doctor can tell you what’s right for you.

How long will it take to lose 10 pounds?

About 10 weeks at 1 pound a week, or 5 weeks at 2 pounds a week, if you lower your calories as you go. Type your own numbers above: the table shows it week by week.

Is 1,200 calories a day enough?

1,200 is the bottom of the range US obesity guidelines use for women’s weight-loss diets; for men it’s 1,500. In the UK, the NHS plan uses 1,400 a day for most women and 1,900 for most men. Very-low-calorie diets, about 800 a day or less, are done only under medical supervision.

Why has my weight loss slowed down?

Because a lighter body burns fewer calories, the same intake makes a smaller deficit over time. NIH research found that at a steady intake, weight takes about a year to get halfway to where it settles. That’s why the calories in the plan go down a little every week.

Is a pound of fat really 3,500 calories?

It’s a rule of thumb. An NIH researcher found it roughly holds for people with more body fat, but it overstates the calories needed per pound for leaner people, because more of what they lose is lean tissue rather than fat.