Calorie Deficit Calculator
Your details
Advanced options
Result
Daily calorie target
- Daily deficit needed
- 500
- Your TDEE (maintenance)
- 2,120
- Your BMR (at rest)
- 1,542
- Weekly deficit
- 3,500
- Eating 1620 calories a day against a maintenance level of 2120 gives a 500 calorie daily deficit, which is about 1 lb a week.
Intake target by rate of loss
What each rate of loss requires, against your maintenance level.
| Rate of loss | Daily deficit | Daily intake | |
|---|---|---|---|
| 0.5 lb / week | 250 | 1870 | |
| 1 lb / week | 500 | 1620 | |
| 1.5 lb / week | 750 | 1370 | below your BMR |
| 2 lb / week | 1000 | 1120 | below the usual floor |
Maintenance by activity level
Your TDEE at each level, so you can see how much the estimate moves.
| Activity level | Multiplier | Maintenance calories |
|---|---|---|
| Sedentary — desk job, little exercise | 1.2 | 1850 |
| Lightly active — 1–3 days a week | 1.375 | 2120 |
| Moderately active — 3–5 days a week | 1.55 | 2389 |
| Very active — 6–7 days a week | 1.725 | 2659 |
| Extra active — physical job or twice daily | 1.9 | 2929 |
How do you calculate a calorie deficit?
To calculate a calorie deficit, work out your total daily energy expenditure by multiplying your BMR by an activity factor, then subtract the deficit you want. A pound of fat holds about 3,500 calories, so a 500 calorie daily deficit produces roughly one pound of loss a week.
BMR = 10w + 6.25h − 5a + s TDEE = BMR × activity target = TDEE − (rate × 3500 ÷ 7)- w
- Weight in kilograms
- h
- Height in centimetres
- a
- Age in years
- s
- +5 for men, −161 for women
- activity
- 1.2 sedentary to 1.9 extra active
- 3500
- Approximate calories in a pound of body fat
The calculation has three stages, and the uncertainty grows at each one. Basal metabolic rate comes from the Mifflin-St Jeor equation, which predicts resting energy expenditure within about 10% for most adults and is the equation the Academy of Nutrition and Dietetics recommends over the older Harris-Benedict. Multiplying by an activity factor gives total daily energy expenditure — and this is the weakest link, because the factors are broad bands and people consistently place themselves one level too high. The final step converts a target rate of loss into a deficit using roughly 3,500 calories per pound of fat, which is where the familiar "500 a day for a pound a week" comes from. That figure is a useful approximation rather than a constant: as you lose weight your BMR falls, so the same intake produces a smaller deficit over time and the target needs recalculating every ten pounds or so.
- Calculate your BMR from weight, height, age and sex.
- Multiply by an activity factor to get maintenance calories.
- Choose a target rate of loss in pounds per week.
- Multiply that rate by 3,500 and divide by 7 for the daily deficit.
- Subtract the deficit from maintenance to get your intake target.
- Recalculate every ten pounds, because BMR falls as you lose.
Worked example: A 32-year-old woman, 80kg at 170cm, lightly active, targeting 1 lb a week
A 32-year-old woman, 80kg at 170cm, lightly active, targeting 1 lb a week
BMR is 10 × 80 + 6.25 × 170 − 5 × 32 − 161 = 800 + 1,062.5 − 160 − 161 = 1,541.5 calories. That is what the body uses at complete rest. Multiplying by the lightly-active factor of 1.375 gives a TDEE of 2,119.6 calories — maintenance. A one pound per week target needs 3,500 ÷ 7 = 500 calories of daily deficit, so the intake target is 2,119.6 − 500 = 1,620 calories. That sits comfortably above both the 1,200 floor and the 1,541 calorie BMR, which is what makes it sustainable. Choosing the moderately-active factor instead would raise maintenance to 2,389 and the target to 1,889 — a 270 calorie difference from one dropdown, which is why honest activity estimation matters more than precision anywhere else in this calculation.
What each calorie deficit input means
- Sex
- Mifflin-St Jeor uses a different constant for each, reflecting average differences in lean mass. It is the only place sex enters the calculation.
- Units
- Which measurement system your figures are in.
- Age
- Your age in years. Resting metabolic rate declines with age, which the equation accounts for.
- Weight
- Your current weight in kilograms. Weigh yourself at the same time of day for consistency.
- Height
- Your standing height in centimetres.
- Weight
- Your current weight in pounds.
- Height (feet)
- The feet part of your height.
- Height (inches)
- The remaining inches.
- Activity level
- Everything you do beyond resting. People consistently overestimate this — if in doubt, pick the level below the one you were about to choose.
- Target rate of loss
- How fast you want to lose. One to two pounds a week is the range most clinical guidance supports; faster costs disproportionately more lean mass.
- Goal weight
- Optional, in the same unit as your current weight. Set it to see a projected timeline. Leave at zero to skip.
What this calorie deficit does not account for
- This is an estimate, not a measurement. Mifflin-St Jeor predicts BMR within roughly 10% for most adults, and the activity multiplier adds more uncertainty on top — treat the number as a starting point to adjust against real results over two to three weeks.
- The 3,500 calories per pound figure is an approximation. It assumes the loss is all fat, whereas early weight loss includes water and some lean tissue.
- BMR falls as you lose weight, so a fixed intake produces a shrinking deficit. Recalculate every ten pounds or progress will stall.
- Activity multipliers are broad bands and most people overestimate. If your weight is not moving at the predicted rate, the activity level is the usual culprit before the arithmetic.
- Not appropriate during pregnancy or breastfeeding, for anyone under 18, or for people with a history of eating disorders.
- Intake floors of 1,200 for women and 1,500 for men are conventions for unsupervised dieting, not safety guarantees. Very low calorie diets need medical supervision.
- Medical conditions and medications materially affect metabolic rate. Thyroid disorders, PCOS, corticosteroids and some antidepressants all change the picture and none are modelled here.
Frequently asked questions
How big a calorie deficit do I need to lose 1 lb a week?
About 500 calories a day. A pound of body fat holds roughly 3,500 calories, so 3,500 divided by seven days is 500. Two pounds a week needs a 1,000 calorie daily deficit, which is harder to sustain.
What is the difference between BMR and TDEE?
BMR is the energy your body uses at complete rest. TDEE is BMR multiplied by an activity factor, covering everything else you do. TDEE is your maintenance level, and the deficit is subtracted from that, not from BMR.
Is a 1,200 calorie deficit safe?
A 1,200 calorie daily deficit is very aggressive and would need a high maintenance level to leave adequate intake. The 1,200 figure usually quoted is a minimum daily intake for women, not a deficit — they are different things.
Why has my weight loss stalled?
BMR falls as you lose weight, so the same intake produces a smaller deficit over time. Recalculate every ten pounds. The other common cause is activity level being estimated too high at the start.
Which BMR formula is most accurate?
Mifflin-St Jeor, which this calculator uses. The Academy of Nutrition and Dietetics found it more accurate than the older Harris-Benedict equation, predicting resting energy expenditure within about 10% for most adults.
Can I lose weight without counting calories?
Yes — a deficit is what matters, not the tracking. Changing food composition, portion size or meal timing can produce one without arithmetic. Counting is simply the most direct way to know whether a deficit exists.
Sources and review
“A new predictive equation for resting energy expenditure in healthy individuals.”
Mifflin-St Jeor: A new predictive equation for resting energy expenditure in healthy individuals — American Journal of Clinical Nutrition (via PubMed)“People who lose weight gradually and steadily are more successful at keeping weight off.”
Healthy weight and losing weight — rate of loss guidance — Centers for Disease Control and Prevention
Last reviewed .