Wetsuit Thickness Picker
What to wear at any water temperature, adjusted for session length and how much you feel the cold — plus why fit matters more than thickness.
The chart
| Water | Suit | Extras | Notes |
|---|---|---|---|
| 24°C+ 75°F+ | Boardshorts or a rash vest | Nothing | Warm enough that sun and chafing are the real problems. A rash vest earns its place for both. |
| 22–24°C 72–75°F | 1 mm top or shorty | Nothing | Borderline. Fine for a short session, chilly for a long one, and wind makes more difference than the water does. |
| 19–22°C 66–72°F | 2 mm shorty or spring suit | Nothing | The classic summer suit. Enough to stop the slow drain of heat on a two-hour session. |
| 17–19°C 63–66°F | 3/2 mm full suit | Optional booties | The most widely owned suit in the world, and the right first purchase for almost anyone. |
| 14–17°C 57–63°F | 4/3 mm full suit | Booties | Cold-water territory. Feet go first, which is why booties appear before gloves and a hood. |
| 11–14°C 52–57°F | 4/3 or 5/4 mm full suit | Booties and gloves | Hands stop working before you notice being cold, and losing dexterity is what ends the session. |
| 7–11°C 45–52°F | 5/4/3 mm hooded full suit | Booties and gloves | A hood roughly doubles your comfortable session length here. Most heat loss is through the head, and this is the temperature where that stops being a saying. |
| -10–7°C 14–45°F | 6/5 mm hooded full suit | Thick booties and gloves | Genuinely cold water. Surf with somebody, keep sessions short, and treat getting changed afterwards as part of the plan rather than an afterthought. |
What the numbers mean
A “4/3” is four millimetres of neoprene through the torso and three in the arms and legs. The body gets the thickness because that is where the heat you need to keep is; the limbs get less because you have to be able to paddle. A suit with the same number everywhere would be either too cold or unwearable.
Fit matters more than thickness. A wetsuit works by trapping a thin layer of water against your skin and letting your body warm it. A loose suit flushes that layer out with every duck dive and replaces it with cold water, which is why a well-fitted 3/2 beats a baggy 4/3 comfortably. It should be genuinely hard to put on.
Extremities go first, and in a predictable order. Feet, then hands, then head — which is why booties appear on the chart before gloves and a hood arrives last. Losing dexterity in your hands ends more sessions than being cold in the body ever does.
Things the chart cannot know
- Wind is worth several degrees. A sunny still day and a 20-knot onshore at the same water temperature are different sessions, and the wind matters most between waves when you are sitting wet in the air.
- Session length changes the answer. You can get away with a thinner suit for forty minutes; two hours in the same water is a different proposition entirely.
- People differ a lot. Body composition, fitness and simple individual variation move the comfortable range by a good few degrees in both directions. If you have always been the first one cold, believe that over the chart.
- Getting changed afterwards is part of it. In genuinely cold water the walk back to the car is where people get properly chilled — a flask and a changing robe do more for the day than another millimetre of neoprene.
How to use
- Check the water temperature, not the air.
- Read the suggested thickness and coverage.
- Adjust for session length and your own tolerance.
- Prioritise fit over buying thicker.
Frequently asked questions
How does a wetsuit actually work?
By trapping a thin layer of water against your skin, which your body warms and the neoprene then insulates. This is why fit matters so much — a loose suit continually flushes warm water out and cold water in, and no amount of thickness compensates for it.
Is a thicker suit always warmer?
Only if it fits. A well-fitting 3/2 is warmer than a baggy 4/3, and thicker neoprene restricts movement and buoyancy in ways that tire you faster. Fit, seam construction and the seal at wrists, ankles and neck matter at least as much as the millimetre rating.
What do the two numbers mean?
Thickness in millimetres at the torso and at the limbs — a 4/3 has 4 mm over the core and 3 mm on the arms and legs. Keeping the core warmer while allowing the limbs to move is the point, since mobility matters most where you bend.
Do seams matter?
Considerably in cold water. Flatlock seams are stitched through and let water in, which is fine in warm conditions. Glued and blind-stitched seams do not perforate the neoprene and are much warmer, and taped or welded seams warmer still — the difference is comparable to a millimetre of thickness.
How long can I stay in?
Far less time than the thickness chart implies for a short session. Heat loss is cumulative, so a suit that is comfortable for 45 minutes may be inadequate at two hours, and repeated sessions in a day compound it. Adjusting for duration is more important than most charts suggest.
When do I need a hood, boots and gloves?
Sooner than most people expect, because extremities lose heat fast and the head is a substantial share of it. Once water is genuinely cold, a hood typically makes more difference than an extra millimetre on the suit. Cold hands also end sessions early by making everything harder.
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