What is hair porosity?

Hair porosity describes how well your hair absorbs and retains moisture. It depends on the condition of the hair cuticle — the outer protective layer. Low porosity hair has a tightly closed cuticle, normal porosity has a healthy cuticle, and high porosity has a damaged or raised cuticle with gaps.

How accurate is the float test?

The float test (placing a clean hair strand in water) is a rough indicator but not perfectly reliable on its own. Product residue, natural oils and water surface tension affect results. This calculator combines multiple tests for a more accurate overall assessment.

Can porosity change over time?

Yes. Chemical services (colouring, bleaching, perming) raise porosity by damaging the cuticle. Heat damage also increases porosity. Virgin hair that has never been chemically treated tends to have lower porosity. Protein treatments can temporarily improve high porosity hair.

Why does porosity matter for hair colour?

High porosity hair absorbs colour quickly but also loses it quickly because the cuticle cannot seal properly. Low porosity hair resists colour uptake and may need longer processing or higher developer volume. Understanding porosity helps stylists adjust formulations for better results.

CutCalcs

Porosity Test Calculator — Hair Porosity Score

Score your hair porosity from multiple test methods and get personalised product and treatment recommendations.

Float Test Result

Place a clean hair strand in room-temperature water

Spray Test Result

Spray water on a dry section of hair

Feel Assessment

How does your dry hair feel to touch?

Air Drying Time

How long does your hair take to air dry?

Chemical History

Previous colour, bleach or chemical treatments

How We Calculate This

This calculator combines five porosity indicators into a weighted score. Each test is rated 1-3 (low to high porosity) and weighted by reliability.

Score formula

Porosity score = Weighted average of all test scores, normalised to 0-100

0-30: Low porosity (cuticle tightly closed)
31-65: Normal/medium porosity (healthy cuticle)
66-100: High porosity (raised or damaged cuticle)

The float test and spray test are weighted highest as they are the most direct indicators of moisture absorption.

Frequently Asked Questions

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Last updated: March 2026

All calculations are estimates. Always perform a strand test before chemical services.