Calorie Calculator for Weight Loss: Resting Energy

Last updated October 27, 2026

Short answer: Resting energy expenditure, the calories your body uses at rest, can be estimated from your sex, age, height and weight with the Mifflin-St Jeor equation. That is your starting point, not a calorie target, because activity adds to it. The old rule that cutting 3,500 calories equals one pound of weight loss overstates the result, according to a 2013 paper in the International Journal of Obesity, so use it only as a rough idea.

Resting energy calculator

The equation

The calculator uses the Mifflin-St Jeor equation, published in 1990 from measurements on 498 healthy adults aged 19 to 78. In metric units:

• Males: 10 x weight (kg) + 6.25 x height (cm) - 5 x age (years) + 5
• Females: 10 x weight (kg) + 6.25 x height (cm) - 5 x age (years) - 161

In that study, the older Harris-Benedict equations overestimated measured resting energy by about 5%.

What this number is not

• It is not your total daily calories. Activity and the energy used digesting food come on top.
• It is not a weight loss target. Ask a clinician before cutting calories sharply.
• It is an estimate for healthy adults in that age range. Medical conditions and medicines can change it.

The 3,500 calorie rule

You may have heard that cutting 500 calories a day makes you lose a pound a week, because a pound of fat holds about 3,500 calories. Hall and Chow explain that this treats the calorie gap as fixed, when in reality it shrinks as your weight falls. They say the rule leads to overestimation of weight loss in individuals and populations, and that correcting the constant alone would not fix it. For a tool that lets you change calories or activity and see how your weight changes, the NIDDK offers a free Body Weight Planner.

What to use instead

• The NIDDK Body Weight Planner, which lets you change calories or activity and see how your weight will change.
• The CDC's 1 to 2 pounds a week as a steady pace to aim for. See how fast to lose weight.
• Percentage of starting weight as your yardstick. See the percentage calculator.

Related: how fast to lose weight, weight loss percentage calculator and protein on a GLP-1.