20 calculators · no signup
Free Fitness Calculators
Data-driven results for the gym, running and weight loss. No fluff — just the numbers and what they mean.
Your TDEE
Lose Fat
1,840
kcal
Maintain
2,340
kcal
Build Muscle
2,740
kcal
Popular
Body & Weight
Calories & Nutrition
Strength & Lifting
Cardio & Heart
Goals
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Fitness calculators that show their work
GymCalc is a free collection of fitness calculators for the gym, running, nutrition and weight loss. Every tool gives you a precise number and explains what it means — no accounts, no apps, and nothing you enter leaves your browser.
The calculators are built on established, published formulas: Mifflin-St Jeor for calories and BMR, the US Navy circumference method for body fat, Epley and Brzycki for one-rep max, the World Health Organization cut-offs for BMI, and the Compendium of Physical Activities for calories burned. You can see every method and its source on the methodology page.
Pick a calculator from the categories above — body and weight, calories and nutrition, strength and lifting, cardio and heart, or goals — switch between metric and imperial, and get your result instantly. Save a result to track it over time, and your stats carry over between calculators so you never enter them twice.
Frequently Asked Questions
Yes. Every calculator is completely free, with no signup, no app to install and no usage limits.
Yes. All calculations run in your browser — the values you enter are never uploaded to or stored on a server.
Established, peer-reviewed formulas such as Mifflin-St Jeor, the US Navy body-fat method, Epley and Brzycki for one-rep max, and WHO classifications. Each method and its source is listed on the methodology page.
Yes. Every calculator has a metric/imperial toggle, so you can work in kilograms and centimetres or pounds and feet.
They are estimates from validated formulas, usually within about 10% for most people. Track your numbers over two to three weeks and adjust based on real-world results.
Yes. The site works on any device and can be added to your home screen to use offline, like an app.