Calorie Calculator | Resting Energy & Activity Scenario

A food calorie is a kilocalorie (kcal), a unit of energy. Energy intake and expenditure are related, but this calculator cannot determine a suitable diet, deficit, surplus or nutrient plan. Such decisions depend on growth, health, reproductive status and other individual factors.

Carbohydrate and protein each provide about 4 kcal per gram, while fat provides about 9 kcal per gram. Those energy values describe food; they do not turn this resting-energy estimate into a meal plan.

For men: REE = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) + 5. For women, use −161 instead of +5. For example, a 30-year-old man at 75 kg and 175 cm gives 1,698.75, rounded to 1,699 kcal/day.

Weight is entered in kilograms and height in centimeters. If you use pounds or inches, the form converts them before applying the equation. The calculation uses the 1990 sex-specific coefficients; it does not use body-fat estimates.

The optional scenario multiplies estimated REE by one chosen factor: 1.2, 1.375, 1.55, 1.725 or 1.9. For a 30-year-old man at 75 kg and 175 cm, REE is 1,699 kcal/day; 1.55 gives 2,633 kcal/day as arithmetic. Days of exercise alone cannot verify a personal activity factor or measured TDEE.

Health Canada and the 2023 National Academies report use life-stage equations and defined physical-activity categories. These five simple multipliers are not those official equations, so choosing one is a transparent assumption rather than an assessment.

Use the result to learn how the equation responds to inputs and assumptions. It is not a calorie intake target or a predicted rate of weight change. Individual assessment needs context beyond these fields; observed weight trends and professional evaluation may inform intake decisions.

Health Canada notes that relative weight stability or change can help evaluate whether intake meets expenditure. One equation result does not establish that balance, especially during growth or changing health.

The original study included healthy people aged 19–78. This calculator accepts that age range and finite positive weight and height. The equation was not derived for children or adults over 78, and separate life-stage equations apply during pregnancy and lactation, and it cannot account for individual medical circumstances.

Blocking an unsupported age prevents a numeric output from appearing more certain than the study permits. Pregnancy and lactation have separate energy-requirement models in the National Academies and Health Canada references.

Measured BMR requires controlled basal conditions. Mifflin–St Jeor estimates resting expenditure from a population equation. Total daily expenditure includes activity and other components, which this form cannot measure or separate.

Daily expenditure may include movement, exercise and the energy cost of processing food. The fields in this form cannot assign credible calorie amounts or percentages to those components.

Weight, height and age do not capture all influences on resting energy. The 1990 equation was fitted to a study sample, so an individual result may differ from measured expenditure. The selected factor adds another unmeasured assumption.

The original paper studied 498 healthy people and reported a population equation, not a guarantee of accuracy for each individual. Error can arise from both the equation and an assumed activity factor.

Sources: Mifflin et al. (1990), original resting-energy equation; National Academies (2023) and Health Canada, life-stage energy-requirement equations and activity categories. Reviewed 29 September 2026.

• Mifflin et al., 1990
• National Academies, 2023
• Health Canada