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Calorie deficit calculator

The famous 3,500-calories-per-pound rule works for the first few weeks, then overpromises, because your body burns less as it shrinks.

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How to use it

  1. Step 1Enter your sex, age, height, weight and activity level.
  2. Step 2Set a goal weight below your current weight.
  3. Step 3Pick a pace from 0.5 to 2 lb a week.
  4. Step 4Read your daily calorie target, weeks to goal and an estimated goal date.

Explainer · 0:21

STEP 1 · RESTING BURN BMR (Mifflin-St Jeor) 1,528 kcal/day woman · 35 · 5 ft 6 in · 180 lb STEP 2 · ADD MOVEMENT BMR + everyday activity × 1.375 2,101 kcal/day = TDEE STEP 3 · SET A DEFICIT TDEE minus 500 −500 1,601 kcal/day target STEP 4 · WHAT TO EXPECT 180 lb ~1 lb a week at first slows over time week 0week 30 0:21 · voiced · captions on
Your body burns energy even at rest. That's your BMR: about 1,528 kcal a day for a 35-year-old woman who is 5 ft 6 in and 180 lb.
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How your daily calories are worked out
Read the transcript
  1. Your body burns energy even at rest. That's your BMR: about 1,528 kcal a day for a 35-year-old woman who is 5 ft 6 in and 180 lb.
  2. Daily movement multiplies it. Light activity is × 1.375, so 1,528 becomes about 2,101 kcal. That's your TDEE.
  3. Eat about 500 kcal less than your TDEE and you're in a deficit: around 1,601 kcal a day.
  4. That's roughly 1 lb a week at first. Loss slows as your body adapts, so treat the number as a starting point and adjust.

From TDEE to a daily target

The tool works out your TDEE with Mifflin-St Jeor and your activity multiplier, then subtracts a daily deficit:

Deficit = pace (lb a week) × 3,500 ÷ 7. So 1 lb a week is a 500 kcal daily deficit, and 2 lb a week is 1,000 kcal.

If the target would fall below 1,200 kcal for women or 1,500 kcal for men, the tool holds calories at that floor and slows the pace instead.

Why the goal date is a best case

As you lose weight, your TDEE falls, and your body adapts by spending a little less energy. Research models like the NIH Body Weight Planner show loss slowing over months even when you eat the same amount.

That's why the date here is optimistic. Recalculate every 10 lb or so, and read Calorie deficit basics for the fuller picture.

Prefer a chart? See How long to lose X pounds: precomputed tables for common inputs.

More weight and calories

TDEE calculator

Calories you burn a day, plus targets to lose, keep or gain

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Protein floor calculator

How much protein keeps muscle while you lose fat

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Macro calculator

Protein, carbs and fat in grams for any calorie budget

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BMI and GLP-1 eligibility

Your BMI and where it sits against label thresholds

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Steps to miles

Distance, time and calories from your step count

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Common questions

How big a calorie deficit is safe?

For most adults, 500 to 750 kcal a day (about 1 to 1.5 lb a week) is a common, sustainable range. Larger deficits are harder to keep and can cost more muscle.

Why am I not losing at a 500 calorie deficit?

Your TDEE estimate may be high, portions may be underestimated, or water retention may hide fat loss. Track a 2 to 3 week average before changing anything.

Is 1,200 calories a day enough?

It's a common minimum for women without medical supervision, but many people need more. Very low intakes make it hard to get enough protein and nutrients.

Does the 3,500 calorie rule work?

It's a fair estimate early on, but it overstates long-term loss because your energy needs drop as you lose weight.

Sources

  1. Mifflin MD et al. A new predictive equation for resting energy expenditure. Am J Clin Nutr 1990
  2. NIDDK Body Weight Planner (NIH)
  3. Dietary Guidelines for Americans