Demystifying the Numbers: Understanding Waterproof Jacket Ratings

The key number to look for on a rain jacket is the hydrostatic head (or HH). This impressively technical sounding term simply refers to the testing machine that measures how much water pressure a fabric can withstand before it starts to leak.

Measured in millimetres (mm), the higher the rating, the more waterproof the jacket. Here's a breakdown of what these ratings typically mean in real-world scenarios:

Below 10,000mm: This is considered water-resistant, not waterproof. Suitable for light drizzle or quick commutes, but not for sustained rain.

10,000mm: This is the minimum range for a jacket to be called "rainproof." It can handle moderate rain showers and wet snow for short periods. (Like our Rainbird)

15,000mm: This is a good choice for most outdoor activities like hiking and camping. It will withstand heavy rain and wet conditions for extended periods. (Like our Skybird)

20,000mm: This is for serious adventurers. Ideal for mountaineering, extreme sports, or prolonged exposure to heavy downpours. (Like our Stormbird)

The ideal waterproof rating depends on your intended use. Here's a quick guide to help you pick the perfect match:

Everyday wear: For light rain or unexpected showers, a 10,000mm rating is sufficient.

Trekking and camping (moderate conditions): Opt for a 10,000mm - 15,000mm jacket to handle unpredictable weather.

While a high waterproof rating is important, breathability is another key factor when selecting a good waterproof. A breathable jacket allows water vapour (sweat) to escape, preventing you from feeling clammy and uncomfortable, so it’s important to look for jackets that mention a breathability rating alongside the waterproof rating.

Our breathability ratings are measured in water vapour passing through the fabric in a set period of time, therefore the bigger the MVTR (moisture vapour transmission rate) we advertise on our garments, the more breathable the fabric is.

The ideal jacket strikes a balance between waterproofing and breathability. Generally, higher waterproof ratings come with slightly lower breathability. Consider your activity level; if you sweat a lot, prioritise breathability.

Over time, dirt and grime can affect the DWR (Durable Water Repellent) coating that provides water repellency. Regularly cleaning your jacket with a technical cleaner and reapplying a DWR treatment (like Nikwax) can extend its lifespan and performance.

By understanding waterproof jacket ratings and considering your needs, you can choose the perfect outer armour to keep you dry and protected on your next adventure. Remember, the numbers are a guide, and real-world factors can come into play. So, stay informed, choose wisely, and don’t let the weather hold you back.