How this calculator works
It estimates resting energy expenditure with the Mifflin–St Jeor equation (Mifflin et al., 1990), using weight in kilograms, height in centimeters and age in years:
- Male equation: 10 × weight + 6.25 × height − 5 × age + 5
- Female equation: 10 × weight + 6.25 × height − 5 × age − 161
The result is multiplied by a conventional activity factor: 1.2 (sedentary: little or no exercise), 1.375 (lightly active: light exercise 1–3 days a week), 1.55 (moderately active: moderate exercise 3–5 days a week), 1.725 (very active: hard exercise 6–7 days a week), 1.9 (extra active: very hard exercise or a physical job). The total is rounded to the nearest 10 calories, because more digits would suggest precision the estimate doesn’t have.
The equation was developed in healthy adults aged 19–78. A systematic review found it more likely than other common equations to come within 10% of measured resting energy use, but individual errors can be larger. The activity factors are broad approximations. The calculator is for adults and isn’t designed for pregnancy, breastfeeding, children or teens, or people with medical conditions that change metabolism.
What goes into a calorie estimate?
Many calculators estimate resting energy needs with a published equation and then apply an activity factor to estimate total daily energy expenditure. Different equations and activity categories give different results. Actual needs vary with individual biology, body composition, activity, health conditions, medications and changes over time. A number that looks exact on a screen is still an approximation.
Maintenance, deficit and surplus
The result is a maintenance estimate: roughly the intake associated with keeping your current weight under these assumptions. Eating below your energy use is a deficit; above it, a surplus. These simple ideas don’t fully predict how any one person responds.
Don’t use a generic calculator to prescribe aggressive restriction. Very low intake may be unsafe. If you take a GLP-1 medication, have a medical condition, are pregnant or breastfeeding, have a history of disordered eating, or aren’t sure what suits you, ask a qualified healthcare professional or dietitian.
Using the result thoughtfully
- Double-check every input and unit.
- Treat the output as a starting estimate, not a strict rule.
- Think about food quality, satisfaction and how you feel, not just a number. Healthy eating guidance emphasizes vegetables, fruits, whole grains and varied protein sources.
- Avoid reacting to every scale fluctuation; weight moves day to day for ordinary reasons.
What this calculator can’t do
It can’t diagnose anything, find a perfect calorie target, account for every medical circumstance or guarantee a weight outcome. Use it as an educational estimate and get professional advice for individual decisions.
