What waterproof rating (mm) do I need for my market and use case?

Waterproof rating measures hydrostatic head - the water column pressure a fabric withstands before leaking (ISO 811). Choosing the right level matters commercially: overspecifying raises fabric cost, underspecifying generates returns.

Practical tiers:

• 5,000mm: light rain, drizzle, urban commuting, wind protection priority. Adequate for shower-proof shells and spring jackets.
• 10,000mm: all-day hiking rain, general outdoor use - the workhorse tier for most hiking ranges and a safe default for mixed European markets.
• 15,000-20,000mm: sustained mountain rain, ski and snow pressure points (seat, knees, pack straps), premium positioning.
• 20,000mm+: expedition and professional use, where marketing claims also matter at retail.

Three things that decide whether the rating survives real use:

• Seam sealing: stitching is the weak point - critical seams must be taped or bonded regardless of rating.
• Breathability: pair the rating with a RET target (RET below 13 is excellent; below 6 for high-output activity) or g/m2/24h figure.
• DWR maintenance: a fluorine-free (C0) DWR keeps the face fabric from wetting out, which preserves breathability in the field.

For Northern European and alpine retail we typically recommend 10,000mm+ for core hiking styles and 20,000mm for technical ski lines; US West Coast and urban programmes can sit lower to protect margin.

Read the full science of waterproof-breathable fabrics.