Free tool

Gray coverage calculator

Enter gray percentage, base level and target level. Get the mix formula, developer and processing time.

This calculator guides you.
Blendsor gives you the exact formula.

With the products you use, the client's history, and a complete diagnosis. Free.

Professional gray coverage guide

Why grays are hard to cover

Gray hair has a different structure: the cuticle is more compact (vitrified) and lacks melanin. This means artificial pigment has more difficulty penetrating and less natural "anchor." This is why mixing a natural base with the desired shade is so effective: the base provides the background pigments that grays lack.

The percentage rule

With less than 25% gray, color works normally. Between 25-50%, add 25% natural base. Between 50-75%, mix half and half. With more than 75%, use 75% natural base. This progression ensures there is always enough background pigment to anchor the desired shade.

Texture and time: the forgotten factors

Hair texture modifies processing time. Fine hair absorbs quickly and can become over-saturated; reduce time by 5 minutes. Coarse hair resists penetration; increase time by 5-10 minutes. In both cases, a strand test saves surprises.

We answer your questions

Frequently Asked Questions

Everything you need to know before getting started

Why does gray hair need a different formula?

Gray hair lacks melanin and has a more closed (vitrified) cuticle, making pigment penetration difficult. Mixing a natural base with the desired shade provides the background pigments needed for lasting coverage.

What developer volume should I use for gray coverage?

In most cases, 20vol (6%) is sufficient. It provides the cuticle opening needed to deposit pigment without excessive lifting. Only use 30vol if you need to lift 2+ levels in addition to covering grays.

What does "natural base" mean in the gray formula?

The natural base is a dye at the same level as the target, but without reflects (only background pigments). It provides the color structure that grays need so the desired shade adheres and lasts.

How long should I leave color on for gray coverage?

Minimum 35 minutes for moderate grays. With 75%+ gray, up to 45 minutes. Coarse hair may need up to 50 minutes. Never less than 30 minutes if you want full coverage.

Does hair texture affect coverage?

Yes. Fine hair absorbs pigment faster and may process in less time. Coarse hair is more resistant and needs more time and possibly a darker natural base level to saturate the fiber.

What is the difference between this calculator and Blendsor?

The calculator gives you the basic ratio and estimated time. Blendsor analyzes 70+ variables (specific brand, color history, porosity, texture) and generates the exact formula with the products you use in your salon.

Have more questions?

Email us at hello@blendsor.com