Recovery calculators
Every recovery calculator — each built on a published, peer-reviewed formula, with the sources cited on the page.
- 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.