Last updated: 3 October 2026
Reviewed by Jordan Morley, FA Level 2 Football Coach
Wetsuit thickness, written as two numbers like '4/3mm', indicates the neoprene thickness on the torso (4mm) and the limbs (3mm) — thicker neoprene on the core for warmth, thinner on the limbs for flexibility. Thickness is matched to water temperature: a 3/2mm suits temperate water (~17-21°C), a 4/3mm cooler water (~14-17°C), and 5/4mm or thicker (plus boots, gloves and a hood) for cold water below ~11°C. A wetsuit works by trapping a thin layer of water that your body heats; the right thickness keeps you warm enough to surf comfortably and safely.
- Two numbers = torso/limb thickness in mm
- Matched to water temperature
- 3/2mm temperate; 5/4mm+ cold water
- Thicker = warmer but less flexible
In practice
Wetsuit thickness (measured in millimetres, often expressed as a combination like 4/3mm for torso/limbs) is matched to water temperature and personal cold tolerance — thicker neoprene provides more insulation but reduces flexibility and paddling efficiency, which is why surfers and open-water swimmers carefully match wetsuit thickness to expected conditions rather than simply choosing the warmest available option.
FAQ
How is wetsuit thickness chosen for water temperature?
Thicker neoprene (e.g. 5/4mm or thicker) suits colder water, while thinner wetsuits (2mm or spring suits) suit warmer conditions — surfers and swimmers typically match thickness to expected water temperature and their personal cold tolerance.
Why not just always wear the thickest available wetsuit for warmth?
Thicker neoprene reduces flexibility and can impair paddling or stroke efficiency, so wearing more insulation than the water temperature requires sacrifices performance without meaningful added benefit.