How Many Calories in a Pound?

About 3,500 calories per pound is the classic estimate for a pound of body-fat tissue, a figure that dates to Wishnofsky in 1958. It's a fair guide for the first few weeks, but it overstates loss over months: as you lose weight your body burns less, so the same diet makes a smaller and smaller deficit (Hall et al. 2011).

Units
Sex
ft
in
lb
Activity level

How do I choose?

Inactive — everyday living only; little or no physical activity at work and no regular exercise. Not the same as bed rest.

Low active — everyday living plus some regular physical activity at work or in your free time.

Active — everyday living plus a good amount of physical activity at work or in your free time.

Very active — everyday living plus a lot of physical activity: a physically demanding job, plenty of exercise, or both.

These four levels come from the National Academies' 2023 report, which split measured adults into quarters from least to most active. The report calls picking your level the hardest step — choose your best guess, then adjust from your real weigh-ins.

Daily deficit

Where the 3,500 number comes from

The rule traces to Wishnofsky (1958), who reasoned that a pound of adipose (body-fat) tissue stores roughly 3,500 calories, so cutting 3,500 calories should cost you a pound (as described by Thomas et al. 2014 and Hall and Chow 2013). In metric that is about 7,700 calories per kilogram.

It was always an estimate for a slab of fat tissue, not a law of physics. The weight you actually lose on a diet is a changing mix of fat, lean tissue, glycogen and water, and — crucially — the arithmetic assumes your body keeps burning the same number of calories the whole way down. It doesn't.

Hall and Chow (2013) note that the rule leads to overestimating weight loss in individuals and populations, because it ignores how energy balance changes during a diet — and that swapping in a corrected number for 3,500 doesn't fix that. Projecting weight over months needs a model that lets your burn fall as you lose.

How many calories are in a pound of fat?

Pure fat stores about 4,280 calories per pound and lean tissue about 820 — the energy densities the NIH model uses (39.5 and 7.6 megajoules per kg; NIDDK model appendix). Body-fat tissue isn't pure fat — it carries water and a little protein — which is why a pound of it comes out nearer 3,500 than 4,280.

Because the weight you lose is a mix, how much energy a lost pound represents depends on your body composition. Hall (2008) found the 3,500-per-pound figure roughly matches the energy in the weight lost only for people starting with more than about 30 kg (66 lb) of body fat; for leaner people it overestimates the deficit each pound takes, because more of their loss is lean tissue.

Composition also explains why the scale drops fast in week one and then slows. Early on, a chunk of the loss is glycogen and the water bound to it rather than fat, so those first pounds come cheap; once that store is drawn down, the weight you shed is a higher share of fat and the pace settles. That is normal, not a stall — the fast start was partly water, and the slower middle is where steady fat loss actually shows up.

What a pound of lost weight is made of One bar split into three parts — fat, lean tissue, and water plus glycogen — showing that a pound of weight lost is a mix, not pure fat. Fat Lean tissue Water + glycogen A pound of lost weight is a mix — its share of fat changes as you get leaner.
A lost pound is a mix of fat, lean tissue, and water plus glycogen — not pure fat.

Worked example

Take a 40-year-old man, 5 ft 10 in (178 cm), 220 lb (99.8 kg), low active, eating 500 below maintenance. His maintenance is about 3,115 calories a day (range 2,776 to 3,454), so his target is about 2,615.

Here is his weight lost by each method, and the calories cut for every pound the model actually loses:

Weight lost by week: NIH model vs the 3,500 rule
WeekNIH model lost3,500 rule lostCut per lb (model)
43.9 lb4.0 lb3,550
1310.0 lb13.0 lb4,549
2617.4 lb26.0 lb5,225
5228.4 lb52.0 lb6,398

In weight terms the model has him at 216.1 lb (98.0 kg), 210.0 lb (95.3 kg), 202.6 lb (91.9 kg) and 191.6 lb (86.9 kg), against the 3,500 rule's 216.0 lb (98.0 kg), 207.0 lb (93.9 kg), 194.0 lb (88.0 kg) and 168.0 lb (76.2 kg).

The first pound goes by day 3 (water and glycogen). His pace drops from about 1.0 lb a week in weeks 1 to 4 to about 0.35 lb a week in weeks 49 to 52, and at that intake the model has him levelling off near 173 lb (47 lb lost) over the following years. The rule keeps marching down at a pound a week.

Read the "cut per lb" column left to right and you can watch the rule break down: at first it costs roughly the promised 3,500 to drop a pound, but by the end of the year each further pound takes far more cutting, because he is lighter and burning less than when he started. Same diet, a smaller and smaller real deficit — which is exactly why the two lines fan apart.

Worked example: NIH model vs the 3,500 rule over 52 weeksLine chart of projected weight in lb over 52 weeks. The solid line is the NIH model (Hall et al. 2011); the dashed line is the 3,500-calorie rule; a dotted horizontal line marks the healthy-range floor for your height, and a line that would cross it stops at the floor, marked with a dot.140160180200220240lb081624324048WeeksHealthy-range floor for your heightNIH model3,500 rule
Worked example (man, 40, 5 ft 10 in, 220 lb, low active, 500-calorie deficit): the NIH model (solid) bends away from the 3,500-rule line (dashed).

What different deficits do in a year

The same man, weight lost in 52 weeks at each deficit (and the daily intake it means):

Weight lost in a year by deficit: NIH model vs the 3,500 rule
Daily deficitEat aboutNIH model3,500 rule
2502,86514.1 lb26.0 lb
5002,61528.4 lb52.0 lb
7502,36543.1 lb78.0 lb
1,0002,11558.2 lb104.0 lb

At 1,000 a day the rule marches him down to 116.0 lb — below the healthy range for his height (the floor is about 128.9 lb at 5 ft 10 in, CDC adult BMI categories) — another sign it overshoots.

In the model, doubling the deficit roughly doubles the one-year loss (28.4 lb at 500 a day, 58.2 lb at 1,000) — but the rule runs ahead every time, by about 12 lb at 250 a day and about 46 lb at 1,000. And the steepest cuts are the ones most likely to push a smaller person's intake below a safe floor. A moderate deficit you can actually hold usually beats a severe one you can't.

So how many calories does it take to lose a pound?

About 3,500 for the first few pounds. Over months it takes more cutting per pound, because your burn falls as you shrink — the rule's biggest error is ignoring that (Hall and Chow 2013). The NIH model turns this into a rule of thumb: every 10 calories a day of lasting change leads to about 1 lb of eventual weight change, with half the change in about a year and 95% in about three years (Hall et al. 2011).

That timeline matters for expectations. Because roughly half of the eventual change takes about a year to appear, the model's curve keeps bending for years. When real dieters stall after a few months, the NIH model's authors point to intake drifting back up rather than the body reaching its new balance (Hall et al. 2011). So when the scale stops, re-measure at your new weight and check what you're actually eating before cutting harder.

Straight-line rule versus the bending model A straight dashed line falls steadily while a solid line starts with it but bends upward, flattening over time. Three labels on the bend read: less weight to move, lower resting burn, the body adapts. 3,500 rule NIH model less weight to move lower resting burn the body adapts weight time
The straight line keeps falling; the real curve bends and flattens.

How many calories to lose 1 or 2 pounds a week

By the rule, 500 a day gives a pound a week and 1,000 a day two pounds. Harvard Health Publishing describes cutting 500 to 1,000 below maintenance for a 1-to-2-lb-a-week pace, a rate experts consider safe. Just expect the pace to fade — the worked example slips from about 1.0 to 0.35 lb a week on a steady 500 — and never eat below 1,200 calories a day (women) or 1,500 (men) without a health professional's supervision. To turn a deficit into a full plan, use the calorie deficit calculator.

In practice, treat any projection as a starting estimate and let the scale correct it. Weigh in over a couple of weeks, compare the trend with the solid model line, and nudge your intake if real life is running faster or slower than the chart. The 3,500 rule is still a useful back-of-envelope check for a short sprint; it's the long, straight-line extrapolation over months that gets people into trouble.

Embed this chart

Running a health or fitness site? You're welcome to embed the chart below, unmodified and with the credit link, on your own pages.

Projected weight over 52 weeks: NIH model vs the 3,500 ruleLine chart of projected weight in lb over 52 weeks. The solid line is the NIH model (Hall et al. 2011); the dashed line is the 3,500-calorie rule; a dotted horizontal line marks the healthy-range floor for your height, and a line that would cross it stops at the floor, marked with a dot.140160180200220240lb081624324048WeeksHealthy-range floor for your heightNIH model3,500 rule
The chart your readers will see — the worked-example comparison, updated with the site.

Frequently asked questions

How many calories are in a pound of fat?

About 3,500 for body fat tissue by the classic estimate; pure fat stores about 4,280.

How many calories do I need to burn to lose a pound?

About 3,500 at first; more over months as your burn falls. In the worked example it works out to about 6,398 per pound averaged over a year.

How many calories are in a kilogram of fat?

The rule works out to about 7,700 per kg; pure fat is about 9,440 per kg.

Why am I not losing a pound a week on a 500-calorie deficit?

Your burn falls as you lose, early losses include water and glycogen, and intake tends to drift upward over time (Hall et al. 2011). More in our guide to being in a deficit but not losing weight.

Is the 3,500-calorie rule wrong?

It's fine for the first weeks and increasingly wrong over months, because it ignores how your burn changes as you lose weight.

Sources

Data as of September 2026. Written by Marko Visic, MPharm. Reviewed October 2, 2026.