Calorie Deficit Calculator

About this calculator

This calculator estimates weight loss from a sustained calorie deficit using the commonly cited rule of thumb that roughly 7,700 kcal of deficit corresponds to about 1 kg of body fat lost (equivalently, about 3,500 kcal per pound). Multiply your daily deficit by the number of days and divide by that constant to get an estimated weight change.

Dietitians, personal trainers, and fitness enthusiasts use this kind of estimate for basic weight-loss planning, but it's important to treat it as a rough approximation rather than a precise prediction — actual fat loss slows over time due to metabolic adaptation, changes in lean mass, and water-weight fluctuations, so real-world results diverge from the simple linear math the longer the deficit is sustained. Enter your daily calorie deficit and the number of days to get an estimate.