Free tools
Science-based tools that translate your measurements into meaningful biological ages — so you can see exactly how your body compares to population averages for your age and sex.
🧬 Biological Age
📏 Body Composition
🔥 Metabolism & Nutrition
❤️ Heart & Exercise
🚬 Lifestyle
Two people who are both 45 years old can have dramatically different biological ages. One might have the cardiovascular system of a 38-year-old, strong aerobic fitness and a healthy body composition. The other might show early signs of metabolic dysfunction, declining lung capacity and arterial changes typical of someone a decade older. Calendar age tells you nothing about this.
Body age calculators translate measurable physiological markers — resting heart rate, blood pressure, lung function, body composition, metabolic rate — into numbers you can actually act on. They answer the question that really matters: how fast is your body ageing relative to your peers?
These calculators use population-based reference data and validated equations. They are educational tools — not medical tests. For a clinical assessment of any health marker, consult your GP.
The most useful approach is to run several calculators and look for patterns. If your metabolic age comes back older than your calendar age, check your body fat percentage and waist-to-height ratio — these together give a far more complete picture of metabolic health than any single metric.
If your heart age is elevated, cross-reference with your VO2 max. Low aerobic fitness is one of the strongest modifiable predictors of cardiovascular mortality, and improving your VO2 max through consistent exercise has a more powerful effect on heart age than almost any other lifestyle change.
Smokers should check both lung age and heart age — smoking ages both organs simultaneously, and even ex-smokers often carry a measurable lung-age penalty that takes years to reverse.
Accuracy varies by calculator type. The BMR calculator is highly accurate — the Mifflin-St Jeor equation predicts resting metabolic rate within about 10% for most adults. Body fat calculators using the US Navy tape-measure method are accurate to within ±3–4 percentage points compared to DEXA scans.
Biological age estimates (metabolic age, heart age, fitness age) are inherently less precise — they are population-based comparisons rather than direct measurements. Think of them as directional indicators, not exact scores. A heart age of 52 when you're 45 is a meaningful signal even if the true value is anywhere from 50–54.
The waist-to-height ratio is particularly well-validated. Dozens of studies confirm it outperforms BMI as a cardiometabolic risk predictor — a WHtR above 0.5 (waist more than half your height) is consistently associated with elevated risk of type 2 diabetes, hypertension and cardiovascular disease regardless of overall body weight.
A result that's older than your calendar age is not a verdict — it's a starting point. Almost every metric measured by these calculators responds to lifestyle change. Metabolic rate increases with muscle mass gained through resistance training. VO2 max improves measurably within 6–8 weeks of consistent aerobic exercise. Blood pressure responds to reduced sodium, increased potassium and weight loss. Lung function in ex-smokers begins recovering within weeks of quitting.
Start with the calculator that feels most relevant to your situation, note your baseline, and retest in 3 months after making targeted changes.