Estimate your functional (fitness) age from physical performance
* Required — fitness norms differ by biological sex.
Educational / wellness tool. Not medical advice.
FitAge combines eight physical-performance tests. Each is calibrated against age in a reference population using the Klemera-Doubal framework; markers that change steeply with age and are low-noise carry more weight.
Maximum hand-grip force — a strong whole-body marker of muscle strength and healthy ageing.
Protocol: Best single-hand squeeze on a hand dynamometer (highest of a few tries).
Modified (knee) push-up repetitions in 40 seconds — upper-body strength-endurance.
Protocol: Knee push-ups, full range, as many as possible in 40 seconds.
Time to stand and sit five times from a chair — lower-body power. Faster (fewer seconds) is better.
Protocol: Arms across chest, 5 full sit-to-stands as fast as safely possible, timed.
Sitting down to and rising from the floor using as little support as possible (0-10). Higher is better.
Protocol: Start at 10; subtract 1 per hand/knee support used, 0.5 per wobble, for sitting and rising.
One-leg standing balance score — a marker of neuromuscular control that declines with age.
Protocol: Stand on one leg, hands on hips; summed best-leg time (cap 120 s).
Forward reach past the toes — hamstring and lower-back flexibility.
Protocol: Seated, straight back, reach forward; cm past (+) or short of (-) the toes.
Waist circumference divided by height — central adiposity. Lower is generally healthier (aim < 0.5).
Protocol: Waist at the navel; both in the same units. Entered as waist + height below.
Simple visual reaction time — processing speed. Faster (lower ms) is better.
Protocol: Mean time to respond to a visual cue, in milliseconds.
Functional age estimates how well your body performs physically compared with others your chronological age. It is built from fitness tests — strength, balance, flexibility, body composition, and reaction time — rather than blood markers.
FitAge adapts the Klemera-Doubal Method (KDM) framework to these functional markers. Each marker is calibrated against age in a reference population, and the markers are combined into a single estimate, regularized toward your chronological age.
Exploratory and educational. Fitness markers are individually weaker age predictors than blood biomarkers, and FitAge has not been validated against health outcomes — it is not a clinical biological-age clock. Reference data are assembled from several population cohorts.
Functional < Chronological
Fitter than typical
Functional ≈ Chronological
Typical for your age
Functional > Chronological
Room to improve
Klemera & Doubal (2006), Mech Ageing Dev — the KDM framework adapted here.
Coefficients assembled from NHANES, Aandstad 2016 (Norway), Mayhew 2023 (CLSA), Araújo 2020 (SRT), and UK Biobank.