Wetsuit Warmth Ratings Explained: Thickness, Seams & What to Look For
Patrick Kirk February 8th, 2023 Posted In: Articles
How Are Wetsuits Rated?
If you’ve ever looked at a wetsuit tag and wondered what 3/2mm, 4/3mm, or 5/4/3mm actually means, you’re not alone. Understanding how are wetsuits rated for warmth is one of the most common questions among surfers, divers, paddlers, and other watersports adventurers.
The short answer is that wetsuits are primarily rated by neoprene thickness, measured in millimeters, with the numbers referring to the thickness of the torso panels followed by the arms and legs.
However, thickness is only one piece of the puzzle. Seam construction, internal liners, neoprene quality, and even how well your wetsuit fits all play a major role in how warm it actually feels in the water.
What is the Rating of My Wetsuit?
So, how are wetsuits rated? The thickness of the neoprene material at different portions of the wetsuit is measured in millimeters. There are several different neoprene thicknesses around your suit. For instance, 6/5/4 is a measurement for frigid cold-water temperatures between 32- and 46-degrees Fahrenheit. 6/5/4 reads as neoprene thickness. 6mm is the rating for the torso, 5mm is for the leg thickness, and 4mm is for the arms.
The rating below the 6/5/4 wetsuit is the 5/4/3, also rated for cold water temps between 44 to 55-degrees. With less thickness comes less insulation, but this cold weather suit still does the job. Then there are thinner wetsuits like the 3/2 and the 2/2. Still holding your body heat, these suits are rated for 59-degree to 71-degree water temperatures. Keep in mind thin wetsuits are more flexible because they use less neoprene.
One of the biggest misconceptions is that a 3/2mm wetsuit means the entire upper half of the suit is 3mm thick while the bottom half is 2mm. That’s not actually how wetsuit thickness works.
Instead, the first number always refers to the torso, where your body loses the most heat, while the second number refers to the arms and legs for increased flexibility. For example:
- 4/3mm: 4mm chest and back, 3mm arms and legs
- 3/2mm: 3mm torso, 2mm arms and legs
- 5/4/3mm: 5mm torso, 4mm legs, 3mm arms
This balance keeps your core warm without sacrificing mobility where you need it most.
Wetsuit Thickness Guide by Water Temperature
| Water Temp | Recommended Wetsuit |
|---|---|
| Below 48°F | 6/5/4mm or 7mm hooded fullsuit + accessories |
| 48–55°F | 5/4/3mm + hood, gloves & boots |
| 55–62°F | 4/3mm fullsuit |
| 62–68°F | 3/2mm fullsuit |
| 68–74°F | 2mm spring suit |
| 74–79°F | 1mm top or rash guard |
| 80°F+ | Rash guard or swimwear |
Keep in mind these recommendations are starting points. Your personal cold tolerance, activity level, wind conditions, and time spent in the water all affect what wetsuit feels comfortable. If you’d like a more detailed breakdown, check out our complete Wetsuit Thickness Guide for more!
Different Types of Wetsuits
Aside from the wetsuit thickness rating is the type of wetsuit. The most popular and probably the most bought wetsuit is the full-body wetsuit. This variation covers the arms down to the wrists and the legs all the way to the ankles. It also covers the neck area. It holds the most heat and is best for SCUBA diving and surfing in colder water temperatures.
If the water is cool, but the air is warm, most choose a spring suit. A spring suit covers the main torso, arms to the elbow, and legs down to the knees. It is not a full-body wetsuit and allows for more ability. The spring suit keeps you warm but leaves your arms and legs exposed to the water.
A long sleeve top wetsuit is ideal for cool or warm water temps. Covering the waist of the torso to the neck and the wrists, the thickness rating for the wetsuit top ranges between 1mm and 2mm.
You can also extend the warmth of almost any wetsuit by pairing it with accessories like a hood, gloves, and booties. Because a significant amount of body heat escapes through your head and extremities, adding these accessories can make a wetsuit feel several degrees warmer without increasing the suit’s neoprene thickness.
What Else Affects Wetsuit Warmth Besides Thickness?
As we’ve briefly discussed throughout this post, there’s more than just thickness that can affect how warm your wetsuit really is.
Seam Construction
The different types of wetsuit seams and their construction can either enhance or hither your overall warmth experience. There are definitely different types of wetsuit seams, but these three are typically the most common:
- Flatlock
- GBS
- Liquid taped
For example, a premium 3/2mm with sealed seams can actually feel warmer than a budget 4/3mm with flatlock stitching. The sealed seams block out cold water from coming in, while the flatlock seams allow some water to slip in.
Internal Lining
We love a good internal lining for a wetsuit. You’ve probably seen these three common types of wetsuit linings when wetsuit shopping:
- Thermal fleece
- Quick-dry linings
- Hollow fiber
Each lining has its own set of pros and cons, so it’s up to you and your needs when choosing a wetsuit for warmth. We’ve got a full guide on understanding wetsuit internal linings for your enjoyment!
Neoprene Quality
Just like with most things in life that you buy, quality is a biggie. And in the case of wetsuits and warmth, neoprene quality makes a big difference. The most common types of material neoprene is made of include:
- Petroleum
- Limestone neoprene
- Yamamoto
If you really want to nerd out on neoprene, neoprene quality, and understanding the materials, check out our post on limestone vs. petroleum neoprene!
Fit
Lastly, fit matters. When it comes to wetsuits and staying warm while wearing one, you’ve got to make sure the fit is just right. It can be a little bit of a Goldilocks moment though – not too tight, not too loose, but just right. That said, a loose wetsuit flushes. Therefore causing cold water to just come right on in. Meanwhile, a super tight wetsuit is restricting, and well, not good for your circulation (needless to say). But a wetsuit that fits just slightly on the tight side will help trap water instead of letting it in.
We’ve got even more details on how tight a wetsuit should fit for you to check out, too!
What Wetsuit is Right for Me?
If you’re wondering what wetsuit fits your need for cold water conditions, it can get tricky to align yourself with a wetsuit that matches your comfort level and maneuverability. When diving in ice-cold weather, go thick with a full body 6/5/4mm. You may notice that this thickness feels stiffer around the body, but if you are floating and swimming slowly to conserve your oxygen tank, the thicker, the better.
If you’re partaking in watersports, this thickness may be too stiff. Shoot for the 5/4/3 if you want more flexibility. But remember, you will not be as insulated, so you may sacrifice time depending on your tolerance for the cold.
If the water isn’t freezing, such as in fall or spring seasons diving or surfing, choose a spring suit with a 3/2 or 2mm spring suit. Ideal for the diver or surfer who needs full arm and leg flexibility. Great for sunny weather with water temps above 60 degrees too. Learn more about how a wetsuit keeps you warm if you want more information on how are wetsuits rated for warmth!
Choosing the Right Wetsuit for Your Activity
Water temperature isn’t the only thing to consider. Your activity level matters too.
For example, surfers constantly generate body heat while paddling, whereas SCUBA divers spend much of their dive relatively still. That means two people in the same 58°F water may require different wetsuit thicknesses.
If you’re unsure between two thicknesses, it’s generally safer to choose the warmer option. It’s much easier to cool down than to end a session early because you’re too cold.
How to Choose the Warmest Wetsuit for Your Needs
When deciding on the warmest wetsuit for your next session, remember that warmth is about much more than neoprene thickness alone. While thickness is the primary way manufacturers rate wetsuits, factors like seam construction, internal thermal linings, neoprene quality, and overall fit all work together to determine how warm you’ll actually stay in the water.
A premium wetsuit with sealed seams, an insulating thermal liner, and a snug fit can often outperform a thicker, lower-quality suit. Likewise, adding accessories like boots, gloves, and a hood can significantly improve warmth in cold-water conditions without requiring you to jump to the thickest wetsuit available.
The best approach is to use a wetsuit thickness guide as your starting point, then consider the water temperature, weather conditions, your activity level, and your personal tolerance for the cold. Whatever waterspot you partake in, choosing the right wetsuit means you’ll stay warmer, more comfortable, and able to enjoy more time in the water!
Frequently Asked Questions on Wetsuit Warmth
What do the numbers on a wetsuit mean?
The numbers on a wetsuit indicate the thickness of the neoprene, measured in millimeters. For example, a 4/3mm wetsuit has 4mm neoprene around the torso for maximum warmth and 3mm neoprene in the arms and legs for improved flexibility. Three-number ratings, such as 5/4/3mm, indicate different thicknesses for the torso, legs, and arms.
What thickness wetsuit do I need for 60°F water?
For most people, a 4/3mm full wetsuit (with sealed seams) is the ideal choice for water temperatures around 60°F. However, your activity level, time in the water, and personal cold tolerance can all affect what feels comfortable. Surfers who generate more body heat while paddling may be comfortable in a 3/2mm suit, while divers often prefer the added insulation of a 4/3mm or thicker suit.
Is a 3/2mm wetsuit warm enough for winter surfing?
It depends on where you’re surfing. A 3/2mm wetsuit is often suitable for mild winter conditions or water temperatures around the low-to-mid 60s°F. In colder climates, most surfers will stay more comfortable in a 4/3mm or 5/4/3mm wetsuit, often paired with boots, gloves, and a hood.
Does a more expensive wetsuit keep you warmer?
Not always, but higher-end wetsuits often include premium features that improve warmth. Better seam construction, thermal internal linings, higher-quality neoprene, and improved fit can all help retain body heat more effectively than a less expensive wetsuit of the same thickness.
What is the warmest type of wetsuit?
For the coldest conditions, the warmest wetsuit is typically a 6/5/4mm or 7mm hooded fullsuit with glued and blind stitched (GBS) or sealed seams, a thermal liner, and a snug, properly fitted design. Pairing your wetsuit with gloves and booties can provide even greater insulation for extended sessions in very cold water.
