Gray Coverage Calculator
The proportion of natural (N) series in a coverage formula tracks the proportion of gray: under 30% gray takes up to a quarter natural, 30–50% takes half, 50–70% takes a half to two thirds, and over 70% takes two thirds to all natural with tone added only for direction. Developer is 20 vol (6%) at every percentage — the thing that changes is the shade split and the time on the head, not the peroxide.
Work out the coverage mix
50–70% gray
30–40 g natural (N) series + 20–30 g tone
That is ½ – ⅔ natural to ⅓ – ½ tone, in 60 g of color.
- Developer
- 20 vol (6%)
- Processing
- Full time, 40 min
Developer is measured separately, at your line’s own ratio — the grams above are the colour half of the mix. Use the mixing ratio calculator for the developer quantity.
The full scale
| Gray % | Natural (N) | Tone | Developer | Processing |
|---|---|---|---|---|
| Under 30% | 0 – ¼ | ¾ – all | 20 vol (6%) | Full time, 35 min |
| 30–50% | ½ | ½ | 20 vol (6%) | Full time, 35–40 min |
| 50–70% | ½ – ⅔ | ⅓ – ½ | 20 vol (6%) | Full time, 40 min |
| Over 70% | ⅔ – all | 0 – ⅓ | 20 vol (6%) | 40–45 min |
| 100% resistant | All N, at or 1 level darker than target | Add for tone only, after coverage is secured | 20 vol (6%) + pre-softening | 45 min from the point the full mix goes on |
A synthesis of the coverage guidance published by the major manufacturer education programmes, expressed in a single scale. Individual brands express the same intent differently. Always strand test resistant gray. Figures last checked 2026-09-06.
Why 20 vol at every percentage
20 vol (6%) is the coverage developer for permanent lines. 10 vol frequently under-covers because it does not open a compacted cuticle; 30 vol tends to lift the pigmented hair past target while it works, so you get coverage and a level you did not ask for.
Color formulation is a chemical service performed by licensed professionals. Always confirm against the instruction sheet in the box you are holding: manufacturers revise formulations, and regional instruction sheets differ. Strand test resistant gray.