WATERPROOF
The first number
Water penetration resistance runs from class 1 to class 4. Class 4 fabric must hold back at least 20,000 Pa of water pressure after pre-treatment.
Check a classWaterproof is not one thing. It is two numbers.
The European standard for rainwear rates a garment twice: how well it keeps rain out, and how well it lets sweat vapour escape. Knowing both helps you pick a jacket for a wet commute or a long, active day out.
- Higher class, more pressure
- Lower Ret, more breathable
- Seams count too
- Small print, drier days
THE SHORT ANSWER
Keep rain out,
let sweat out.
EN 343 rates rainwear on two scales.
The first number is rain, the second is breathability.
BREATHABILITY
The second number
Breathability is measured as Ret, a resistance to water vapour. The lower the Ret, the more breathable the fabric; class 4 means Ret 15 or less.
See the numbers
SEAMS
Stitches leak first
The standard tests seams as well as fabric. For class 4, the seams must also reach 20,000 Pa after pre-treatment by cleaning.
What to look for
FOUR THINGS TO LOOK FOR
Read past
the word waterproof.
None of these needs a lab. They are about reading the label and the inside of the jacket before you pay.
Find the pictogram
An EN 343 garment carries a pictogram with two class numbers: water penetration first, breathability second.
Match the class to the day
A short wet commute and a long, active day in the hills ask different things. Higher classes were tested to higher pressures.
Check the seams
Look inside for taped or sealed seams. The standard tests seams separately because stitch holes can let water through.
Ask about the finish
Look for a PFAS-free or fluorine-free water repellent. Research found the best ones repel rain as well as short-chain fluorinated finishes.
TWO NUMBERS WORTH KNOWING
Pressure in,
vapour out.
The top waterproof class,
and the top breathability class.
≥ 20,000 Pa
Minimum water pressure, fabric and seams
Class 4 was added in BS EN 343:2019. Both the fabric and the seams are tested after pre-treatment, and must hold at least 20,000 pascals.
WATERPROOF · EN 343 CLASS 4
≤ 15 Ret
Maximum water vapour resistance
Ret is measured in m²Pa/W. Class 1 is above 40, class 2 above 25 up to 40, class 3 above 15 up to 25, and class 4 is 15 or less.
BREATHABILITY · EN 343 CLASS 4
The standard's own note: all classes can result in a restricted wearing time. Even a breathable jacket can feel damp inside during hard effort.
A QUICK LABEL CHECK
What does
the class mean?
Pick the water penetration class on an EN 343 label to see the pressure the fabric was tested to. The bar shows how demanding the test is.
Based on the BS EN 343:2019 class tables as summarised by a protective clothing maker. 1,000 Pa is about 102 mm of water.
THE BEADING FINISH
Why raindrops
roll off.
Many shells have a durable water repellent finish that makes drops bead and roll away. For years these finishes used fluorinated chemicals (PFAS), which are very persistent in the environment.
In September 2024 the European Commission adopted a restriction on PFHxA and related substances, covering consumer textiles such as rain jackets and waterproofing sprays, with transition periods of 18 months to 5 years depending on the use.
In conversation
Questions people ask
What does EN 343 mean on a jacket?
It is the European standard for protective clothing against rain, snowflakes, fog and ground humidity. The label shows a class for water penetration resistance and a class for breathability.
How do pascals compare with millimetre ratings?
One protective clothing maker's guide gives 1,000 Pa as roughly 102 mm of water, so the 20,000 Pa needed for EN 343 class 4 is about 2,040 mm.
What is a Ret value?
Ret is the resistance of a fabric to water vapour passing through it, in m²Pa/W. The lower the number, the more breathable the fabric. EN 343 class 4 breathability is Ret 15 or less.
Are PFAS-free jackets as good in the rain?
A 2019 Leeds and Stockholm study found the best non-fluorinated repellents gave water repellency equal to short-chain fluorinated ones. They repelled oils far less well, which matters mainly for some workwear.
Why does the inside of my jacket feel wet?
Sweat vapour needs to escape through the fabric. EN 343 notes that every breathability class can still limit how long a garment can comfortably be worn.
Sources
Each figure on this page comes from the sources below.
- Skanwear: Understanding EN 343 rain protection (BS EN 343:2019 classes)
- European Commission: Commission restricts use of a sub-group of PFAS chemicals (2024)
- University of Leeds: Outdoor and protective clothing 'should be greener'
- Schellenberger et al., Journal of Cleaner Production: fluorinated chemicals in functional textiles (abstract)
- Met Office: Rain