Wetsuit Thickness: What 3/2 Means and Which You Need
A 3/2 wetsuit is 3 mm thick at the torso and 2 mm at the arms and legs; O'Neill suggests a 3/2 or 4/3 for water around 55 to 64°F.
By Adolph GreenContributing writer.
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The short answer
Wetsuit thickness is given in millimeters of neoprene. Thicker neoprene holds more warmth but bends less. Match the suit to the water temperature where you swim, surf or dive, then adjust for how cold you run and how long you stay in.
What does 3/2 mean on a wetsuit
Two numbers mean the suit uses two thicknesses. O'Neill explains that the first number is the torso, where your core needs the most warmth, and the second is the arms and legs, where thinner neoprene lets you move. A 3/2 is 3 mm at the body and 2 mm at the limbs. A 4/3 is 4 mm and 3 mm, and a 5/4 is 5 mm and 4 mm. A single number, such as 2 mm, means the same thickness throughout.
Wetsuit thickness temperature chart
O'Neill publishes this suggested guide for water temperature:
| Water temperature | Suggested suit |
|---|---|
| 80°F and up (26°C and up) | UV rash guard, no wetsuit |
| 71 to 79°F (21 to 25°C) | 1 mm top |
| 65 to 70°F (18 to 20°C) | 2 mm, often a shorty |
| 55 to 64°F (12 to 17°C) | 3/2 or 4/3 full suit |
| 48 to 54°F (8 to 11°C) | 4/3 or 5/4 full suit |
| 40 to 47°F (4 to 7°C) | 5/4 or 6/5 with a hood |
| Below 39°F (below 3°C) | 6/5 or 7 mm with a hood |
O'Neill marks the chart as a reference only. Body type, activity level and air temperature all change what feels right. Wind and long sessions make you colder; hard paddling keeps you warmer.
What thickness wetsuit do I need
- Look up the usual water temperature for your spot and season.
- Find the row in the table above.
- Go one step thicker if you get cold easily, stay in for hours, or face wind. Go one step thinner if you run warm or stay very active.
Thickness is not the only factor. Fit matters too: a suit should sit close to the skin, because water that flushes through a loose suit carries warmth away. The colder rows of the chart also show hooded suits, so consider boots and gloves for that water as well. O'Neill also rates its own suits for warmth by how the seams are built, so two suits of the same thickness can feel different.
Wetsuit styles
- Full suit: covers arms and legs. In the O'Neill chart, every suit from 3/2 up is a full suit.
- Shorty (spring suit): short arms and legs, for warm water.
- Tops and pants: separates for layering or warm days.
Of the 78 wetsuits listed under sports and outdoors on Wiki Shopping on October 26, 2026, 34 are full suits, 10 shorty suits, 10 pants and 9 tops. By thickness, 16 list 2 mm, 14 list 3 mm and 6 list 2.5 mm.
How we count
Style and thickness are read from each store listing on Wiki Shopping. Wetsuits that do not state them are left out of those counts, and the counts change as listings are added or removed.