Calorie Needs Calculator

How the estimate is calculated

The tool first estimates resting energy using Mifflin–St Jeor, then multiplies it by a commonly used activity factor. Activity categories are rough and self-reported, so the result should be treated as an estimate.

Activity multipliers used

The selectable factors are 1.2 (sedentary), 1.375 (light), 1.55 (moderate), 1.725 (very active) and 1.9 (very highly active). These conventional calculator categories are rough assumptions, not factors validated in the original Mifflin–St Jeor study. They describe the overall day, not the calories from one workout.

For published whole-day activity ranges and an explicit uncertainty interval, use the TDEE calculator. These two tools can differ because their activity assumptions differ.

Why calorie needs vary

Actual energy expenditure can vary with body composition, movement, training, illness, pregnancy, environment and measurement error. Weight change over time can also indicate that an estimate is too high or too low for an individual.

Not a weight-loss prescription

This calculator does not automatically prescribe a calorie deficit or surplus. People with medical conditions, eating disorders, pregnancy or specialized nutrition needs should use individualized professional guidance.

Related tools

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BMR Calculator

Estimate the energy your body uses at rest throughout the day.

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TDEE Calculator

Explore your total daily energy estimate, including your usual activity.

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Macro Calculator

Turn calories and your chosen split into carbohydrate, protein and fat grams.

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References & sources

1. Mifflin MD, St Jeor ST, et al. Resting energy equation.

Sources checked and page updated on 19 September 2026. This tool is for general educational use and is not a diagnosis or personal medical prescription.