Calories to fat calculator

Choose a direction. To turn calories into body fat, enter a calorie total, such as a weekly deficit. To find the calories in an amount of body fat, enter the fat in pounds or kilograms. Add a number of days to see the daily amount.

This is an energy conversion, not a weight-loss forecast. The 3,500 kcal rule treats every pound lost as the same tissue and ignores the way energy use falls as weight falls, so real loss over weeks and months is slower than the rule predicts. For a forecast, use a dynamic model such as the weight planner.

By the common rule, a pound of body fat holds about 3,500 calories (kcal). A kilogram holds about 7,716 kcal, often rounded to 7,700. The figure goes back to Max Wishnofsky's 1958 estimate of the energy in body weight that is gained or lost.

Calories to body fat, 3,500 kcal per pound

Body fat to calories

The rule is a fair way to convert an amount of energy into an equal amount of body weight. It is a poor way to predict weight loss. As you lose weight, your body uses less energy, so the same daily deficit removes less weight each week than it did at the start.

Kevin Hall and colleagues at NIDDK offered a simpler rule of thumb for an average overweight adult: every 100 kJ (about 24 kcal) of sustained daily change in intake eventually changes body weight by about 1 kg. Body weight responds slowly, with about half of that change in the first year. The table compares both rules for a deficit kept up every day. The first-year column is half of the eventual change. These are rough averages: your own change depends on your size and body fat.

Daily deficit: 3,500 kcal rule vs Hall rule of thumb

For a personal forecast that adjusts as your weight changes, use the weight planner on this site or the NIDDK Body Weight Planner. Both use dynamic models instead of a fixed number of calories per pound.