Waterproof Ratings Explained: Performance, Pressure and Breathability

Waterproof ratings define how a jacket performs when conditions stop being forgiving, when rain becomes sustained, wind drives water under pressure, and exposure lasts hours rather than minutes.

Since the 1960s, our outerwear has been developed for prolonged exposure at sea, where salt, wind, movement and time place far greater demands on waterproof protection than everyday use on land.

This guide explains how waterproof ratings work, how they are measured, and what level of protection is genuinely appropriate for different conditions. For a broader overview of fabrics, construction types and aftercare.

A man in a boat with a waterproof jacket, waterproof salopettes, navy beanie and sailing gloves

Men's Waterproof Jackets

Person sailing in waterproof jacket adjusting ropes on deck at sea.

Women's Waterproof Jackets

What Are Waterproof Ratings?

A waterproof rating indicates how much water pressure a fabric can withstand before moisture penetrates it. The rating is expressed in millimetres (mm) and is based on controlled testing.

For example, a fabric rated at 10,000mm can resist a column of water ten metres high before leaking. The higher the number, the greater the resistance to water pressure. Waterproof ratings describe fabric performance only, real-world protection depends equally on construction, seam integrity and how the jacket is used.

Explore our men’s waterproof jackets designed for different levels of exposure and use.

How Waterproof Ratings Are Measured

Waterproof performance is measured using the hydrostatic head test. A fabric sample is secured beneath a column of water, and pressure is gradually increased until moisture passes through the material. The height at which this occurs determines the rating.

While this provides a reliable benchmark, it does not fully replicate real conditions. Offshore, water is driven horizontally by wind, forced through seams by movement, and applied continuously. This is why waterproof ratings must always be considered alongside garment design and intended environment.

How Waterproof Ratings Translate to Real-World Performance

Waterproof ratings describe how much water pressure a fabric can withstand in testing, but their real value lies in how they translate to performance in use. At Henri-Lloyd, these ratings are applied deliberately, based on the demands each jacket is designed to face.

Henri-Lloyd jackets are worn and tested by professional sailors and brand ambassadors in some of the world’s most demanding marine environments, providing real-world validation of performance under prolonged exposure.

See an outline of ratings below:

Rating	Protection Level	Description
10,000mm	Light to Moderate Exposure	Jackets rated at 10,000mm are suitable for light to moderate rain and shorter periods of exposure. This level of protection performs well in changeable weather where breathability and comfort are prioritised alongside waterproofing.
15,000mm	Sustained Wet Conditions	At 15,000mm, waterproofing becomes more dependable in prolonged rain. This rating is appropriate for extended outdoor use, coastal sailing and environments where exposure lasts hours rather than minutes.
20,000mm	High-Pressure, Prolonged Exposure	Ratings of 20,000mm and above are reserved for conditions where water is driven under pressure by wind, movement and duration. This level of protection is required offshore, where jackets are exposed continuously to rain, spray and salt.
25,000–30,000mm	Professional Grade Waterproofing	Intended for prolonged offshore use where garments are subjected to sustained pressure from driving rain, heavy spray, and repeated movement. At this level, fabrics are designed to resist water ingress not only from rainfall but from localised pressure caused by leaning, kneeling, and equipment contact. Garments built to this standard are suited to long passages and demanding watch systems, where exposure is continuous and failure is not an option.

Front view of a Henri-Lloyd offshore sailing jacket with high collar, multiple pockets and protective hood.

Waterproof vs Water-Resistant vs Water-Repellent

Waterproof jackets are designed to prevent water ingress entirely, using membranes, sealed seams and protective construction.

Water-resistant garments repel light moisture but will allow water through under pressure or prolonged exposure. Water-repellent fabrics rely on surface treatments that cause water to bead but offer minimal protection in sustained rain.

For serious wet-weather use, only fully waterproof construction is appropriate.

Breathability and Waterproofing: Finding the Right Balance

Waterproofing alone does not guarantee comfort. Without breathability, moisture generated inside the jacket cannot escape, leading to condensation and overheating.

Breathability is measured using Moisture Vapour Transmission Rate (MVTR), which indicates how efficiently vapour passes through a fabric. Higher values improve comfort during movement and prolonged wear.

In demanding environments, waterproof protection must be balanced with breathability to remain wearable over time, a principle central to Henri-Lloyd’s performance outerwear design.

Why Construction Matters

Waterproof ratings measure fabric performance, but real-world protection comes from how each layer works together. As shown in the image, the outer fabric repels water and wind, while the internal membrane blocks moisture under pressure and allows heat vapour to escape. A protective lining shields the membrane from wear, maintaining breathability over time.

Seams, closures and high-stress areas remain the most common failure points, which is why fully taped seams, protected zips and durable water-repellent finishes are essential. Without this level of construction, even high-rated fabrics cannot deliver consistent protection in prolonged, exposed conditions.

Choosing the Right Waterproof Rating

Selecting the correct waterproof rating depends on duration of exposure, weather intensity, activity level and environment. Understanding these factors allows you to choose protection that performs reliably rather than optimistically.

FAQ'S

What does a waterproof rating mean on a jacket?

It measures how much water pressure a fabric can withstand before leaking, expressed in millimetres.

Is 20,000mm waterproof enough for heavy rain?

Yes, ratings at this level are designed for prolonged exposure and high-pressure conditions, for most extreme sailing conditions you may need to consider jackets with 25,000m+.

Is a higher waterproof rating always better?

Not necessarily. Waterproof ratings are only one factor in overall performance. Higher ratings are often paired with more robust construction, which can add weight or bulk. The most effective jacket is one specified for the conditions you actually face.

Do seams affect waterproof performance?

Yes, fully sealed seams are essential for consistent protection.