Recovery calculators
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.
Recovery & wellness guides
Evidence-tiered explainers on popular recovery practices — what the research actually supports, and what’s marketing.
- Cold Water Immersion: Benefits, Evidence and How to Start
What ice baths and cold plunges actually do — separating the well-supported effects from the hype.
- Sauna Therapy: Benefits, Evidence and How to Use It
Among the better-supported recovery practices — here's what the evidence shows, and where it stops.
- Compression Boots: Benefits, Evidence and How to Use Them
What pneumatic compression boots actually do for recovery — the real effects versus the marketing.
- Massage Guns (Percussive Therapy): What the Evidence Says
What percussive massage devices do for soreness and range of motion — and what they don't.
- Red Light Therapy (Photobiomodulation): Benefits and Evidence
What red and near-infrared light therapy is claimed to do — and where the evidence actually stands.
- Optimising Your Sleep Environment: Temperature, Light and Sound
The bedroom factors that genuinely affect sleep — and the gadgets that mostly don't.
- Breathwork for Recovery and Stress: What the Evidence Shows
What breathing techniques can and can't do for stress, recovery and focus — honestly assessed.
- Foam Rolling & Mobility: Benefits and Limits
What foam rolling actually does for mobility and soreness — and the myths worth dropping.