FitCalcs
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Free & private

Health & fitness
calculators

12 calculators for weight goals, body composition, nutrition and training — each runs in your browser using a published formula and shows its method.

Runs offlineShows its formulaNothing uploaded

Body composition

Energy & nutrition

Fitness

Pregnancy

How to use these together

The nutrition tools are a chain. Your BMR is the energy you burn at rest; multiply it by an activity factor to get your TDEE (maintenance calories); adjust that up or down for a goal with the calorie calculator; then split the target into protein, carbs and fat with the macro calculator. The BMI and body fat calculators give you a starting point and a way to track composition, not just weight.

For training, the one-rep-max calculator turns a set you have done into percentage-based work targets, and the running pace calculator converts a time and distance into pace and projected race times.

Frequently asked questions

Are these health calculators accurate?
Each uses a published, peer-reviewed formula — Mifflin-St Jeor for BMR, the U.S. Navy method for body fat, Devine and Robinson for ideal weight, Naegele's rule for due dates, Epley and Brzycki for one-rep max. The maths is exact; the inputs (your measurements, activity level) carry the uncertainty. Every tool shows its formula and assumptions.
Is my data private?
Yes. Every calculator runs entirely in your browser. Nothing you type is sent to a server or stored. You can disconnect from the internet after the page loads and the tools still work.
Which calculator should I start with?
For weight goals, work through BMR → TDEE → Calorie → Macro in that order: they build on each other. For a body-composition snapshot, use BMI plus the body fat calculator. For training, the one-rep-max and running pace tools set your work targets.
Do you give medical advice?
No. These are informational tools. Categories, ranges, and targets are general guidance based on formulas and population data, not a substitute for a doctor, dietitian, or trainer who knows your history.

For informational purposes only, not medical advice. Consult a healthcare professional before making health decisions.