How to Choose Waterproof and Breathability Ratings for Outerwear

Waterproof and breathability ratings need to be considered together when shopping for outerwear. You’ll often find them specified like 10k/15k where the first number is the waterproof rating and the second is the breathability rating. A 10k/15k jacket is therefore moderately waterproof and breathable. Something like 5k/15k would be a low waterproof jacket but moderately breathable.  The higher the numbers the more waterproof and breathable the outerwear is rated.

Read on for specific information on waterproof and breathability ratings.

What are waterproof ratings?

Waterproof rating is measured in millimeters (mm). It relates to a laboratory measurement method that tests the pressure required for the water to begin to leak through the fabric. The higher the number the more waterproof the fabric is considered. You’ll find waterproofing ratings ranging from 5,000 mm to greater than 20,000 mm. This is often expressed by manufacturers as 5k, 10k, 15k, 20k…etc.

Resistance to Moisture Ranges:

  • Less than 5,000 mm offer little to none
  • 5,000-10,000 mm is low resistance
  • 10,000-15,000 mm is moderate resistance
  • 15,000-20,000 mm is high resistance
  • Greater than 20,000 mm is very high resistance

What are breathability ratings?

Breathability is measured in grams (g). It relates to a standardized laboratory measurement method that measures the weight of water vapor passing through an area of fabric over 24 hours. Like breathability manufacturers often express these ratings as 5k, 10k, 15k, and 20k. Which can be a little confusing if you don’t understand how these numbers combine to form the overall waterproof/breathability rating of the jacket.

Breathability Ranges:

  • Less than 5,000 g is low breathability and will hold sweat against your body and you will eventually feel chilly when you stop moving
  • 5,000-10,000 g is low breathability and is the minimum you’ll want to consider
  • 10,000-15,000 g is moderate breathability and acceptable for most conditions
  • 15,000-20,000 g is high breathability
  • Greater than 20,000 g is very high breathability
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