About FitnessCalculator.info
Numbers you can check, not just trust
FitnessCalculator.info is a small set of fitness calculators built around one idea: a result is only useful if you can see how it was reached.
Why we built this
Most online calculators give you a number and nothing else — no formula, no source, no sense of how confident you should be in it. We built FitnessCalculator.info the opposite way. Every calculator on this site shows its methodology in plain language on the same page as the tool, with a worked example you can check by hand if you want to. If we can't explain how a number was reached, we don't publish it.
What's on the site
Thirteen calculators covering body composition, calorie targets, strength training and cardio — each sourced from a named published formula:
- BMI calculator — WHO body mass index classification
- BMR calculator — Mifflin-St Jeor resting metabolic rate
- TDEE calculator — activity-adjusted daily energy expenditure
- Macro calculator — protein, carb and fat targets from a calorie goal
- Body fat calculator — US Navy circumference method
- Ideal weight calculator — Devine, Robinson, Miller and Hamwi formulas
- Calorie deficit calculator — evidence-based deficit and surplus options
- One rep max calculator — Brzycki, Epley and Lombardi estimates
- Protein intake calculator — ISSN and sports science ranges by goal
- Waist-to-hip ratio calculator — WHO cardiovascular risk thresholds
- VO2 max calculator — George et al. non-exercise prediction formula
- Pregnancy weight gain calculator — IOM 2009 guidelines
- Running pace calculator — pace, speed and race finish time predictions
How calculations are made
Every calculator uses an established, peer-reviewed or clinically published formula — not a proprietary algorithm. Sources include the WHO BMI classification, the Mifflin-St Jeor equation, the IOM 2009 pregnancy guidelines, the George et al. VO2 max non-exercise formula, the ISSN protein intake recommendations, and the US Navy circumference method. Each calculator page names its source and shows the formula in full. Where a formula has known limitations — and they all do — we state them plainly on the same page, under a dedicated Limitations section.
Who this is for
Anyone who wants a fast, free, private read on their own numbers — whether you're starting a fitness routine, adjusting your nutrition, or just curious. Our calculators are built for adults; they're not a substitute for individualized advice from a doctor, registered dietitian, or qualified coach, and we say so on every results page.
Our commitment
- Clarity — every formula is shown on the page, not hidden behind the result.
- Accessibility — every calculator works with a keyboard, a screen reader, and a small phone screen.
- No dark patterns — no fake countdown timers, no forced sign-ups, no result hidden behind a paywall.
- Honesty about limits — health formulas are estimates derived from population averages, and we say that plainly rather than implying false precision.
A note on accuracy
Every result on FitnessCalculator.info is an estimate based on established formulas and general population data. None of our tools diagnose a medical condition or replace individualized advice from a qualified healthcare professional. If a result concerns you, or doesn't match what you'd expect, please treat it as a starting point for a conversation with a doctor or dietitian — not a final answer.
Questions or corrections
If you've spotted an error, have a question about a formula, or want to suggest a new calculator, we want to hear about it. Visit our Contact page or email contact@fitnesscalculator.info.