Every butterfly starts as a caterpillar.
Free, accurate fitness calculators to measure where you are, plan your next crawl, and track the metamorphosis. No sign-up, no downloads — every calculation runs right in your browser.
The calculators
🔥TDEE CalculatorYour true daily calorie burn, plus calorie targets for cutting, maintaining and bulking.📉Calorie Deficit CalculatorDaily calorie target to reach your goal weight by your target date — with pace warnings.⚖️BMI CalculatorBody mass index, your WHO category, and the healthy weight range for your height.📏Body Fat CalculatorBody-fat percentage from a tape measure (US Navy method), with fat mass and lean mass.📐Waist-to-Height RatioThe WHO-backed “waist under half your height” check for central fat and health risk.🎯Ideal Body Weight CalculatorYour ideal body weight (IBW) from four clinical formulas, plus the healthy BMI range.🏋️1RM CalculatorEstimate your one-rep max from any hard set, with a percentage training-load chart.🥗Macro CalculatorTurn your daily calorie target into protein, carb and fat grams — and per-meal amounts.🍗Protein CalculatorYour daily protein target range by goal, with real-food equivalents.💧Water Intake CalculatorDaily water target from your body weight, training load and climate.☕Caffeine Half-Life CalculatorHow much of that coffee is still in you at bedtime — timeline included.🏃Running Pace CalculatorPace per km and per mile, speed, and full split tables for any race distance.🏁Race Time PredictorTurn a recent 5K or 10K into predicted times for every race up to the marathon.❤️Heart Rate ZonesYour five training zones from age and resting heart rate (Tanaka + Karvonen).😴Sleep CalculatorBedtimes and wake times on 90-minute sleep cycles, so you wake between cycles.
Why Caterpillar?
- Published formulas, not vibes. Mifflin-St Jeor, the US Navy tape method, Epley & Brzycki, Devine and friends — every calculator names its formula and its honest error bars.
- Private by design. Everything runs locally in your browser. No accounts, no cookies, nothing uploaded. Read the privacy policy — it is two paragraphs, because there is nothing to hide behind.
- Free forever. Tools this simple should not have paywalls or login walls.
Start with one number
Transformations fail from complexity, not lack of information. Pick one calculator, learn your number, act on it for two weeks, then re-measure. Small crawls compound.