33 calculators · every formula cited · free, no sign-up
Evidence-based fitness
FitTools builds every calculator on published, peer-reviewed formulas — with the sources cited on the page, so you can check our working.
An endless, source-checked feed of fitness, recovery and longevity facts — like the ones that click, save the keepers, filter to what you care about.
Open Pulse →New · coming soon
Know your numbers — at-home blood test
Test the biomarkers behind your heart, metabolic and biological age — results flow straight into your dashboard and auto-fill the calculators that use them.
New · a fresh one every day
Play today’s Ballpark
Guess a real, cited fitness stat in one move — then test yourself on the weekly myth-buster quiz. Build a streak, learn the numbers.
Start with the big four
All 33 tools →- Fuel
2,711 kcal
TDEE Calculator
How much fuel you actually burn — before you cut, bulk or panic.
- Strength
116.7 kg
One-Rep Max
Big number energy, no spotter required. Epley, Brzycki & friends.
- Fuel
144 g protein
Macro Calculator
Protein, carbs and fat targets that match the goal, not the influencer.
- Strength
Z2 112–131 bpm
Heart-Rate Zones
Five zones, one chart, zero guessing — Zone 2 included.
Nutrition
Calculators for energy needs, macros and body composition — every formula cited to its published source.
- TDEE Calculator — Total Daily Energy Expenditure
Estimate your total daily energy expenditure (TDEE) and BMR with the Mifflin–St Jeor, Katch–McArdle or revised Harris–Benedict equations. Free, no sign-up.
- Macro Calculator — Protein, Fat & Carb Targets
Free macro calculator: set protein by bodyweight (1.6–2.2 g/kg, per Morton et al. 2018), choose a fat percentage, and get gram and calorie targets for each macro.
- Calorie Deficit Calculator — Weight-Loss Timeline
Free calorie deficit calculator: estimate weekly weight loss and a timeline to your goal using the 7,700 kcal/kg heuristic, with a safety cap at 25% of your TDEE.
- BMI Calculator — Body Mass Index & WHO Category
Free BMI calculator with WHO categories (underweight to obesity class III), metric and imperial inputs, and an honest explanation of BMI's limits for muscular and athletic builds.
- Body Fat Calculator — US Navy Circumference Method
Free body fat calculator using the US Navy circumference method (Hodgdon & Beckett 1984). Tape-measure inputs, metric and imperial, with the ±3–4 point error band shown honestly.
- Ideal Weight Calculator — Devine, Robinson, Miller & Hamwi
Free ideal weight calculator reporting the range across the Devine, Robinson, Miller and Hamwi formulas, framed honestly as historical estimating equations rather than health targets.
- BMR Calculator — Basal Metabolic Rate
Free BMR calculator using Mifflin–St Jeor (default), Katch–McArdle and revised Harris–Benedict equations, with clear guidance on which to trust.
- Lean Body Mass Calculator — Boer Formula
Free lean body mass calculator using the Boer formula, with an optional body-fat override for a direct calculation. Metric and imperial.
- FFMI Calculator — Fat-Free Mass Index
Free FFMI calculator (fat-free mass index) with the Kouri height adjustment — the muscularity metric from the classic study of steroid-free bodybuilders.
- Water Intake Calculator — Daily Hydration Guideline
Free water intake calculator based on EFSA adequate intakes (2.0 L women / 2.5 L men total water) with an exercise allowance from published sweat-rate ranges.
- Calories Burned Calculator — MET Method
Free calories burned calculator using the MET method (kcal/min = MET × 3.5 × kg ÷ 200) with activity values from the Compendium of Physical Activities.
- Steps to Calories Calculator
Free steps-to-calories calculator: stride length from your height, distance from your steps, and energy from published walking MET values. Clearly labelled as a rough estimate.
- Creatine Calculator — Loading & Maintenance Dose
Free creatine dosage calculator: optional loading at 0.3 g/kg/day for 5–7 days and 3–5 g/day maintenance, per the ISSN position stand (Kreider 2017).
Strength
Training calculators: one-rep max, plate loading, progression planning and strength standards.
- One-Rep Max Calculator — Epley, Brzycki & More
Free 1RM calculator using the Epley, Brzycki, Lombardi and O'Conner formulas, with a 50–95% of 1RM loading table for programming your training.
- Barbell Plate Calculator — Load the Bar Right
Free barbell plate calculator: enter a target weight and bar, edit your plate inventory, and get the per-side stack — plus the nearest achievable load when the exact weight can't be made.
- Warm-Up Sets Calculator — Barbell Ramp
Free warm-up set calculator: a bar ×10, 40% ×5, 60% ×3, 80% ×1 ramp to your first work set, every step rounded to plate-loadable weights.
- Double Progression Planner
Free double progression planner: hit the top of your rep range on every set to add load and reset reps; otherwise repeat the load and chase reps. Clear next-session prescriptions.
- Training Volume Calculator — Tonnage & Weekly Sets
Free training volume calculator: per-exercise tonnage (sets × reps × load) and weekly hard-set counts per muscle group, the volume measure used in hypertrophy research.
- Strength Standards — How Strong Are You?
Free strength standards tool: classify your squat, bench press or deadlift from physically active to elite using Kilgore's published performance standards tables.
- DOTS Calculator — Wilks & IPF GL Points
Free DOTS calculator with Wilks and IPF GL points, using official coefficients from the OpenPowerlifting codebase and regression-tested against real meet results.
Recovery
Sleep, heart-rate and recovery calculators grounded in published research.
- Heart Rate Zone Calculator — Tanaka & Karvonen
Free heart rate zone calculator using the Tanaka equation (208 − 0.7 × age) and the Karvonen heart-rate-reserve method, with a full five-zone training table.
- Sleep Calculator — When To Go To Bed
Free sleep cycle calculator: enter your wake-up time and get bedtime options for 4, 5 or 6 full 90-minute cycles, including 15 minutes to fall asleep.
- Running Pace Calculator — Pace, Speed & Splits
Free running pace calculator: min/km and min/mile pace, speed, and kilometre splits for any distance from 400 m to ultra distances.
- Race Time Predictor — Riegel Formula
Free race time predictor using the Riegel formula (T₂ = T₁ × (D₂/D₁)^1.06): predictions for 5k, 10k, half marathon and marathon from any recent result.
- Caffeine Half-Life Calculator
Free caffeine half-life calculator: chart how a dose decays over 24 hours (C(t) = dose × 0.5^(t/t½)) and when it drops below your chosen sleep threshold.
- Phenotypic Age Calculator — Biological Age from Blood Tests
Free Phenotypic Age (PhenoAge) calculator using the peer-reviewed Levine 2018 model: nine blood biomarkers plus age, with the exact published coefficients and full methodology shown.
- Heart Age Calculator — Your Cardiovascular Age from PREVENT
Free Heart Age calculator built on the AHA PREVENT equations (2024). Enter your blood pressure, cholesterol and health history to see your 10-year cardiovascular risk and heart age, with ApoB and Lp(a) shown as context.
- CGM Metrics Calculator — GMI, Time in Range & Variability
Free CGM metrics calculator: Glucose Management Indicator (GMI), time in range and glucose variability (%CV) from your own readings, using the international consensus definitions. Runs entirely in your browser.
- Healthy Lifestyle & Life Expectancy — The Evidence
How five healthy-lifestyle factors related to life expectancy at 50 in the landmark Li 2018 study: people with all five lived, on average, 12–14 years longer than those with none. Population association, not a prediction.
- Metabolic Fitness Index — Open, Transparent Score
Free open-methodology Metabolic Fitness Index: combines time in range, glucose variability, GMI, waist-to-height and resting heart rate into a transparent 0–100 score with a full sub-score breakdown. Not a medical test.
- Pace of Aging Index — Open Lifestyle-Trajectory Score
Free open-methodology Pace of Aging Index: a transparent 0–100 lifestyle-trajectory score from fitness, activity, waist-to-height, sleep, heart rate and habits, with a full sub-score breakdown. Not a biological age or medical test.
- Recovery Readiness Index — Open, Self-Relative Score
Free open-methodology Recovery Readiness Index: a transparent daily 0–100 score comparing today's HRV, resting heart rate, sleep and breathing rate to your personal baseline. Self-relative, not a medical test.
Labs
Advanced tools with enhanced disclaimers — arithmetic only on values you supply, and no advertising.
- Peptide Reconstitution Calculator
Reconstitution calculator for research and prescribed peptides: concentration from vial and diluent, draw volume and U-100 units from your prescribed dose. Arithmetic only — no dosing guidance.