Active & Functional - New York ← Back to site

Free Tool

Your calorie
estimate range.

Built on the Mifflin-St Jeor equation — one of the best-validated equations for estimating resting energy expenditure in the general population — with Katch-McArdle available if you know your body fat %. Shown as a range, because a single number would imply more precision than any formula can deliver.

I know my body fat % (switches to the Katch-McArdle formula, based on lean body mass)
Plus: physically demanding job, or training twice a day

Estimated daily maintenance

— kcal
calories per day
— —

Formula breakdown

Mifflin-St Jeor
—
Estimated resting energy expenditure (RMR) from age, sex, height & weight. In validation research it fell within ±10% of measured values for about 82% of nonobese adults — closer to 70% in adults with obesity.
Katch-McArdle
—
Estimated resting energy expenditure from lean body mass. May be more informative when body fat % is measured accurately — an inaccurate body fat estimate can make it less reliable, not more.

Adjust for your goal

Lose weight
—
Maintain
—
Build muscle
—
The real test is the next 2–4 weeks, not this number. This is a starting estimate, not a measurement. The range shown is a practical uncertainty allowance, not a statistically validated interval — your true daily burn varies more than any formula can capture, and the activity adjustment is an informed judgment call. Research on activity and metabolism (Pontzer's Constrained Energy Model) also suggests the body partially compensates as activity increases, so very active people often burn less extra than standard adjustments imply. Eat near this number for two to four weeks, track your real-world trend — weight, energy, performance — and adjust based on what actually happens. Your own data beats any equation.

Estimates only — not medical or clinical nutrition advice. This tool is not intended for anyone under 18, during pregnancy or breastfeeding, with a history of disordered eating, or with a medical condition requiring clinically managed nutrition. The activity adjustment (1.2–1.9) is a widely used practical heuristic, not a clinically validated instrument, and this tool does not account for daily step count, session duration, or occupational activity, which also affect your true expenditure. Formulas: Mifflin-St Jeor (1990) and Katch-McArdle (lean-mass based). Consult a registered dietitian or physician for individualized guidance.