Fitness math, minus the guesswork
Free calculators for calories, macros, protein, body fat, heart-rate zones, and more — powered by real published formulas, not vibes.
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Fourteen tools covering nutrition, body composition, training, and cardio. Pick one and get your numbers in seconds.
TDEE Calculator
Find your daily calorie needs for losing, maintaining, or gaining weight.
🥗Macro Calculator
Split your calories into protein, carbs, and fat targets that fit your diet.
🥩Protein Calculator
How much protein you actually need per day, based on your weight and goal.
⚖️BMI Calculator
Check your Body Mass Index and what category you fall into.
📏Body Fat Calculator
Estimate body fat % with the U.S. Navy tape-measure method.
🧬BMR Calculator
Your basal metabolic rate — calories burned at complete rest.
🎯Ideal Weight Calculator
A healthy target weight range for your height (Devine formula).
🏋️One-Rep Max Calculator
Estimate your 1RM and get % training tables (Epley formula).
⏱️Calories Burned Calculator
How many calories your workout really burns (MET method).
💧Water Intake Calculator
Your daily hydration target in liters and glasses.
❤️Heart Rate Zone Calculator
Your 5 training zones from max heart rate (Tanaka formula).
🏃Running Pace Calculator
Pace, speed, and finish-time predictions for any distance.
📏Waist-to-Hip Calculator
WHR — a better health signal than BMI alone (WHO cutoffs).
⚡Creatine Dosage Calculator
Loading and maintenance doses personalized to your weight.
Why FitMath Lab?
Most fitness calculators are buried in pop-ups or locked behind email gates. We built the opposite:
- Real formulas. Every tool documents the exact equation it uses — Mifflin-St Jeor, Epley, Tanaka, the Navy method — so you know where your numbers come from.
- Private by design. Calculations happen in your browser. Nothing you type is sent anywhere or stored.
- Fast and free. No accounts, no paywalls, no 2,000-word preamble before the tool. The calculator is always at the top of the page.
Frequently asked questions
Are these calculators really free?
Yes — every calculator on FitMath Lab is free, with no account or sign-up. The site is supported by ads and affiliate links.
How accurate are the calculators?
Each tool uses published, peer-reviewed formulas (Mifflin-St Jeor, Epley, the Navy method, and others). They’re estimates — typically within 10–15% of lab measurements — and excellent starting points.
Do I need to create an account?
No. Everything runs in your browser; we don’t collect or store your inputs.
Can I trust the supplement recommendations?
Our “picks” boxes only feature well-researched staples like whey protein and creatine monohydrate. They’re affiliate links, clearly labeled, and never affect the calculator results.