Wetsuit thickness and water temperature chart
The industry sizes neoprene in two numbers — a 4/3 is 4 mm through the torso and 3 mm in the arms and legs, so you stay warm where it counts and can still bend where you need to. This is the standard mapping.
| Water °C | Water °F | Thickness | Suit type | Boots / gloves / hood |
|---|---|---|---|---|
| 25 + | 77 + | None | Boardshorts or rash vest | None |
| 22–25 | 72–77 | 2 mm | Spring suit or neoprene top | None |
| 20–22 | 68–72 | 2/2 | Spring suit or shorty | None |
| 17–20 | 62–68 | 3/2 | Full suit | None |
| 14–17 | 57–62 | 3/2 | Full suit | Boots optional |
| 11–14 | 52–57 | 4/3 | Full suit | 3 mm boots, gloves optional |
| 8–11 | 46–52 | 5/4 | Full suit + hood | 5 mm boots, 3 mm gloves |
| 5–8 | 41–46 | 5/4 | Hooded full suit | 5 mm boots, 5 mm gloves |
| Below 5 | Below 41 | 6/5 | Hooded full suit | 7 mm boots, 5 mm gloves |
Air temperature is not the number that matters. A 12 °C sea on a sunny 25 °C day is still a 12 °C sea, and it will take heat out of you at exactly the same rate. Size from the water, then let wind and session length adjust it.
Why two surfers in the same water need different suits
A chart assumes an average person having an average session. Three things genuinely move the answer, and the calculator applies all of them.
How you feel the cold
This is the big one, and it is not a character flaw. Body composition, circulation and simple habituation vary enormously. Someone who feels the cold badly is effectively surfing water two or three degrees colder than the thermometer says. If you are always the first one in from a session, size up a step rather than assuming you will toughen up.
How long you stay in
Heat loss is cumulative. A 45-minute dawn patrol in a 3/2 can be perfectly comfortable in water where a three-hour session would leave you shaking. If you regularly surf past the two-hour mark, take the warmer option — the extra flexibility of a thinner suit stops being worth much once you are too cold to paddle properly.
Wind
You are only submerged part of the time. Sitting on the shoulder in an offshore breeze, wet, is where most of the cold actually arrives. A windy day in 14 °C water feels closer to 12 °C, which is the difference between a 3/2 and a 4/3.
What the two numbers actually mean
A 4/3 has 4 mm neoprene on the torso and 3 mm on the limbs. The core is where your body most needs to keep heat, and the arms and shoulders are where you most need to move — thicker neoprene resists every paddle stroke, so shaving a millimetre off the limbs buys back a lot of flexibility for very little warmth.
Some suits list three numbers, like 5/4/3: torso, legs, then arms. Same logic, one step further.
Thickness is not the whole story either. A well-sealed 3/2 with taped seams and a good neck will keep you warmer than a loose, flushing 4/3, because most heat is lost through water moving in and out rather than through the neoprene itself. Fit matters at least as much as millimetres — which is why the wetsuit size chart is worth reading before you buy.
Seams, zips and why cheap suits feel colder
Three seam types, in ascending order of warmth and price:
- Flatlock — stitched right through the neoprene. Flat, comfortable, and it lets water in. Fine above about 17 °C, cold below it.
- Glued and blind-stitched (GBS) — glued, then stitched only part-way through, so there are no holes. The standard for 3/2 and 4/3 suits.
- Taped or liquid-sealed — GBS plus an internal seal over the seam. What you want in a 5/4.
Zips matter too. A chest zip flushes far less than a back zip and is warmer for the same thickness, at the cost of being more awkward to get into. Zip-free suits are warmer again, and more awkward still.
Frequently asked questions
What thickness wetsuit do I need?
Size it from water temperature. Roughly: 2 mm or a spring suit above 22 °C, a 3/2 full suit from 17–20 °C, a 4/3 from 11–14 °C, and a 5/4 with a hood below 11 °C. Then adjust for how you feel the cold, how long you stay in and whether it is windy — those three can easily move you a full step.
Should I get a 3/2 or a 4/3 wetsuit?
The crossover sits around 14 °C. Above that a 3/2 is warm enough for most people and noticeably easier to paddle in. Below it, take the 4/3. If you surf right on the line, choose by session length: a 3/2 for short surfs, a 4/3 if you are regularly out past two hours. If you can only own one and your water swings through the year, the 4/3 is the more useful suit.
What does 4/3 mean on a wetsuit?
Four millimetres of neoprene on the torso and three on the arms and legs. The thicker core keeps heat where your body most needs it, while the thinner limbs preserve the flexibility you need to paddle. A 5/4/3 simply splits it three ways: torso, legs, arms.
What is the 120 rule for wetsuits?
A rough rule of thumb where you add the air temperature and the water temperature in Fahrenheit — if the total is under about 120, wear a wetsuit. It is a quick sanity check rather than a sizing method, and it does not tell you which thickness. Use water temperature for the actual decision.
Do I need boots, gloves and a hood?
Boots start being worth it around 14 °C and become necessary below about 12 °C. Gloves follow at roughly 11 °C, and a hood below about 10 °C. Your head and hands lose heat fast, and cold hands end sessions sooner than a cold torso does — if you are cutting surfs short in winter, add gloves before you buy a thicker suit.
Is a thicker wetsuit always warmer?
No. Fit and seam quality often matter more. A loose suit flushes cold water through on every duck dive, and no amount of neoprene fixes that. A well-fitted 4/3 with sealed seams will beat a baggy 5/4 every time.
Next steps
- Wetsuit size chart — get the fit right, which matters as much as the thickness.
- What to wear under a wetsuit — and what not to.
- Surfboard volume calculator — a thicker winter suit adds a little float, too.