Calculate your BMI and ideal running weight range — and see how weight affects your running performance.
Under 18.518.5–2525–3030+
Healthy weight range
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kg (BMI 18.5–25)
Optimal running weight
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kg (BMI 19–22)
Weight to lose/gain
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to reach optimal range
Body weight per cm
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kg/cm (elite ~0.37–0.40)
Performance impact of weight
⚠️ This is an estimate only. BMI is a population-level screening tool, not a precise measure of individual health or fitness. It does not account for muscle mass, bone density, body fat distribution, or ethnicity. A muscular runner may show as "overweight" while carrying very little fat. Use this as a rough guide only — not a health diagnosis.
BMI and running
BMI is a blunt tool — it doesn't account for muscle mass, bone density, or body composition. Elite runners typically have BMIs of 18–21. However the best indicator of running fitness is not BMI but running economy — how efficiently you use oxygen at a given pace. That comes from technique, not just weight.
The OYF perspective: Natural running technique with minimalist footwear changes your body composition over time. Stronger feet, activated glutes, and better posture all contribute to a leaner, more efficient running body — without crash diets or obsessing over the scales.
More accurate ways to assess body composition:
1. DEXA scan — the gold standard for body composition. An X-ray scan that precisely measures fat mass, lean muscle mass, and bone density across different body regions. Available at sports clinics and some hospitals. Costs roughly £80–£150. Results are highly accurate and repeatable.
2. Hydrostatic (underwater) weighing — you are weighed submerged in water. Fat floats, muscle sinks — the difference gives a very accurate body fat percentage. Less commonly available but considered one of the most accurate methods.
3. Skinfold calipers — a trained professional measures fat thickness at several body sites. Cheap, quick, and reasonably accurate (within 3–4%) when done by an experienced tester. Available at most gyms and sports science departments.
4. Smart scales (bioelectrical impedance) — send a small electrical current through the body to estimate fat and muscle. Convenient but can vary significantly with hydration levels. Better for tracking trends over time than for absolute values.
5. Waist-to-height ratio — a simple and surprisingly accurate health indicator. Divide your waist circumference by your height (both in the same unit). A ratio below 0.5 is considered healthy for most adults. More predictive of cardiovascular risk than BMI alone.