Race Weight Calculator

How race weight is calculated

The calculator assumes you should lose fat while keeping muscle. Your lean mass is derived from current weight and body fat, then projected at the target body fat: race weight = lean mass / (1 − target %). Every extra kilogram costs a runner roughly 2.5–3 s/km and a cyclist real watts on every climb.

Healthy limits

Lighter isn't always faster. Below 5% body fat for men and 12% for women, hormones, immunity, recovery and bone density suffer (RED-S syndrome). Competitive amateur marathoners typically race at 8–12% (men) and 16–20% (women) — and you shouldn't hold that year-round: peak at race weight for your key events.

Frequently asked questions

How do I find my current body fat percentage?

DEXA scans are the most accurate. Practical options are calipers or the US Navy circumference method — compute it in our body fat calculator and plug the result in here.

How fast can I safely lose weight?

0.25–0.5 kg per week — a deficit of roughly 300–500 kcal per day. Faster than that you start losing muscle and training quality. Keep weight stable during hard training blocks and in the final 2 weeks before racing.

Should I cut for every race?

No. Race weight is a peak state for 2–4 key events per year. Living at minimal body fat year-round wrecks your hormonal balance and ultimately slows you down.