The first number is the neoprene on the body, the second the thinner panels on the arms and shoulders, in millimeters. The bands below are what most surfers wear; go one step warmer if you run cold, surf dawn patrols, or sit in the wind between sets, and one step thinner for a sealed, modern suit or a short summer session.
| Water | Suit |
|---|---|
| 72 °F and up | Boardshorts or a rash guard; a 1 mm top for wind |
| 65–72 °F | 2 mm springsuit or top |
| 60–65 °F | 3/2 mm fullsuit |
| 54–60 °F | 4/3 mm fullsuit |
| 47–54 °F | 5/4 mm fullsuit, hooded or with a separate hood |
| below 47 °F | 6/5 mm hooded fullsuit |
Water temperature matters more than air. A sunny 70 °F day over 55 °F water is still a 4/3 day. Check a buoy or the local forecast for the sea temperature, not the beach forecast.
Zip style changes warmth as much as a millimeter does. A chest zip or zipperless suit lets in less water than a back zip, so a good 3/2 chest zip can feel like a cheap 4/3. Hooded suits and separate hoods add real warmth, since most heat leaves through the head. Booties and gloves come in at about 54 °F for most people.
Thinner suits paddle better. If you surf a lot in the same water, buy the thinnest suit you can stay warm in and add a hood and boots before going up a thickness.