Fitness Age Calculator

How It Works

Your "fitness age" is an estimate of how old your body acts based on fitness markers rather than the calendar. This concept is backed by research from the HUNT Fitness Study in Norway, which found that cardiorespiratory fitness (measured by VO2max) is the strongest predictor of longevity. The key inputs are resting heart rate (lower is better — elite athletes are often below 50 bpm), waist circumference (a proxy for visceral fat), and exercise frequency and intensity. A resting heart rate above 80 bpm is associated with a 45% higher risk of death compared to below 60 bpm. Regular moderate-to-vigorous exercise can lower your fitness age by 5-10 years. The good news is that fitness age responds quickly to lifestyle changes — just 8 weeks of consistent exercise can produce measurable improvements.