Free Fitness & Health
Calculators
Science-backed tools for calories, body composition, strength training, and more. Built on peer-reviewed formulas. No accounts. No paywalls. Just answers.
TDEE Calculator
Find your Total Daily Energy Expenditure and get personalized calorie and macro targets for fat loss, maintenance, or muscle gain.
BMI Calculator
Calculate your Body Mass Index using both the standard and height-corrected New BMI formula. See your healthy weight range instantly.
Body Fat Calculator
Estimate your body fat percentage using the U.S. Navy method and BMI-based formula. All you need is a measuring tape.
One Rep Max Calculator
Estimate your one-rep max from any weight and rep count. Get a full percentage-based training table for programming workouts.
Water Intake Calculator
Find your optimal daily water intake based on body weight, activity level, and climate. Includes a full hydration schedule.
Why use FitCalculator?
Science-backed
Every calculator uses peer-reviewed formulas from published research. We cite our sources and show multiple methods.
Instant results
All calculations run locally in your browser. No loading spinners, no server calls, no waiting.
Private by design
We never see, store, or transmit your data. Your numbers stay on your device and disappear when you close the page.
Works everywhere
Designed mobile-first and tested across devices. Use it at the gym, in the kitchen, or at your desk.
Completely free
No sign-ups, no paywalls, no premium tiers. Every calculator is free and always will be.
Multiple formulas
We never rely on a single equation. See results from multiple methods so you get a range, not a guess.
How it works
Pick a calculator
Choose the tool that matches your goal — whether it is tracking calories, estimating strength, or checking body composition.
Enter your numbers
Input basic info like weight, height, and age. All data stays in your browser and is never stored.
Get your results
See instant results from multiple scientific formulas, with clear explanations and actionable next steps.
The complete toolkit for fitness planning
Whether you are just starting your fitness journey or fine-tuning an advanced training program, having accurate numbers makes all the difference. FitCalculator brings together the most essential health and fitness calculators in one place, all powered by the same equations used by nutritionists, strength coaches, and medical professionals.
Our TDEE calculator uses the Mifflin-St Jeor equation, widely considered the gold standard for estimating daily energy expenditure, to give you personalized calorie and macronutrient targets for any goal. The BMI calculator provides both the classic formula and the newer height-corrected version developed by Oxford mathematician Nick Trefethen. Our body fat calculator combines the U.S. Navy circumference method with the Deurenberg BMI-based estimate for a more reliable two-method average.
For strength training, the one rep max calculator averages five established formulas — Brzycki, Epley, Lander, Lombardi, and O'Conner — and generates a complete percentage-based training table for programming your workouts. The water intake calculator goes beyond the generic "8 glasses a day" advice by adjusting recommendations for your body weight, exercise habits, and local climate.
Every tool is designed to be fast, private, and transparent. Calculations run entirely in your browser with zero server calls. We show our formulas, cite our sources, and display results from multiple methods so you always see the full picture rather than a single number. And because we believe good health tools should be accessible to everyone, FitCalculator is and will always be completely free.
Built for real people
We designed FitCalculator for the person standing in their kitchen wondering how many calories they need, the gym-goer trying to figure out their working sets, the runner checking if they are drinking enough water, and the parent who just wants a quick health check without navigating pop-ups and paywalls. Our tools are mobile-first, load instantly, and work on any device.
FitCalculator is not a replacement for professional medical advice. Our calculators provide estimates based on population-level formulas, and individual results will vary. For personalized guidance, we always recommend consulting a qualified healthcare provider, registered dietitian, or certified trainer. But as a starting point for understanding your own body and setting informed goals, these tools are as good as it gets for free.