What is the natural pH of hair?

Healthy hair has a natural pH of 4.5-5.5, which is mildly acidic. This acidic mantle keeps the cuticle flat and smooth, protecting the inner cortex. Products within this pH range are considered hair-friendly. The scalp has a slightly higher natural pH of around 5.5, which helps maintain its protective acid mantle.

Why do chemical services need alkaline pH?

Alkaline products (pH 8+) open the hair cuticle, allowing chemicals to penetrate the cortex where they can change the hair structure. Permanent colour needs to penetrate to deposit pigment and alter melanin. Bleach needs access to melanin to destroy it. Perms need to reach disulphide bonds to reshape them.

What does pH mean for hair colour longevity?

After colouring, using acidic products (pH 4-5) closes the cuticle and locks colour molecules inside the cortex. Alkaline shampoos open the cuticle, allowing colour to wash out faster. Using a pH-balanced, sulphate-free shampoo between pH 4.5-5.5 helps maintain colour vibrancy for longer.

How do I restore hair pH after chemical services?

After alkaline chemical services, use an acidic conditioner or pH-balancing treatment (pH 3.5-4.5) to close the cuticle and restore the natural acid mantle. Apple cider vinegar rinses (diluted) are a traditional method. Most professional post-service conditioners are formulated at low pH specifically for this purpose.

CutCalcs

pH Calculator — Hair Product pH & Cuticle Effects

Understand pH levels of hair products and their effect on the hair cuticle.

Product Type

How We Calculate This

This calculator shows the typical pH level of different hair products and explains their effect on the hair cuticle and cortex.

The pH scale

The pH scale runs from 0 (strongly acidic) to 14 (strongly alkaline), with 7 being neutral. Each whole number represents a 10x difference in acidity or alkalinity.

pH 0-4: Acidic — closes cuticle, hardens hair
pH 4.5-5.5: Natural hair pH — ideal maintenance range
pH 7: Neutral — water
pH 8-10: Alkaline — opens cuticle for chemical processing
pH 11-14: Strongly alkaline — maximum penetration, risk of damage

Frequently Asked Questions

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Last updated: February 2026

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