Triathlon Wetsuit Selection Calculator

Wetsuit legality in triathlon isn't a single universal rule — it's set by whichever governing body sanctions your race, and the thresholds genuinely differ. This calculator encodes three rulebooks: ITU/World Triathlon draws the line at 20°C for mandatory use and separates elite cutoffs (22°C banned) from age-group cutoffs (24.5°C optional, 28.8°C allowed-but-ineligible-for-awards, above that banned); USAT uses flat 22°C (elite) and 28.3°C (age-group) optional/banned splits with no in-between "allowed but unranked" tier; and Ironman/WTC follows its own 24.5°C / 28.8°C bands. Get the governing body and competitor type wrong and you'll get a legality answer that doesn't apply to your actual race, so check your event's specific rules if precision matters.

Independent of legality, recommended neoprene thickness drops in steps as water warms — 5mm below 14°C down to swimskin-or-none above 25°C — reflecting that thicker neoprene traps more heat and adds more buoyancy, but also more overheating risk. The buoyancy time-savings estimate scales with that same thickness tier — roughly 3.1 seconds per 100m at 2mm up to about 5.5 seconds per 100m at a full 5mm suit, dropping to zero once the water is warm enough that the calculator recommends a swimskin or no suit at all — reflecting the field-observed rule of thumb that wetsuits reduce drag by holding your hips and legs higher in the water; it's a coarse average, not a guarantee for any individual swimmer's body position. Finally, the hypothermia and hyperthermia risk scores move in opposite directions across the same temperature scale — cold risk falls as thermal risk climbs — so read both together rather than treating either alone as the full safety picture.