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How much developer for your colour?
A misread ratio, a rough measuring cup, and the colour doesn’t hold or shifts. This calculator does the rule of three for you: the colour you weigh, the ratio on the tube, and you get the grams of developer, the split between two shades and the total to prepare.
To weigh
60 gof developer · 120 g of mix in totalIn the bowl
60 g of colour, then 60 g of developer, weighed on a scale zeroed after each addition.
The method
How it is calculated
Three multiplications you can redo at the basin.
- Developer = colour × ratio. At 1:1.5, 60 g of colour needs 90 g of developer.
- Shade 2 = colour × share of the second shade. Shade 1 = the rest.
- Total = colour + developer. That is what the bowl has to weigh at the end.
- The other way round: for a wanted total, colour = total ÷ (1 + ratio). 100 g at 1:1 is 50 g of colour and 50 g of developer.
The calculation assumes colour and developer weigh the same per millilitre, which is nearly true for creams. Manufacturers give their ratios by weight or by volume depending on the line: the tube always has the last word.
Three rules
What makes a colour hold
The three habits colourists mention to us before they even talk about shades.
- 01
Weigh, don’t measure
A measuring cup reads to the nearest 5 ml and developer foams; a kitchen scale zeroed between each addition gives the gram. On 60 g of colour, 10 g of developer too many dilutes the pigments and the grey coverage.
- 02
Volume is not ratio
The developer volume (10, 20, 30, 40) says how much it lifts: 3, 6, 9 or 12% peroxide. The ratio says the quantity. You choose the volume for the result, the ratio for the brand, and you never compensate one with the other.
- 03
Write the formula down
Shades, shares, ratio, volume, processing time: the formula that worked has to be found again at the next visit, by you or a colleague. In Napiro it goes in the client’s technical record, with her private photos.
Read on
Questions
What we are asked about mixing
What ratio for my brand?
According to the instructions and product sheets consulted on 30 October 2026: Wella Koleston Perfect, Schwarzkopf Igora Royal and Goldwell Topchic mix at 1:1 for standard shades; L’Oréal Majirel at 1:1.5. High-lift shades and lighteners often go to 1:2. Check the tube or the leaflet: they are what counts, not this table.
How much colour for long hair?
For a regrowth, half a tube to one tube (30 to 60 g of colour) is usually enough. For thick mid-back lengths, count one and a half to two tubes. Better to mix a second bowl during processing than to throw away half of the first: the mix does not keep.
Can I keep the leftover mix?
No. As soon as the developer touches the colour, the reaction starts and the mix loses its power in about thirty minutes. The colour alone, tube closed, keeps; that is why weighing precisely avoids waste.
How do I find the formula again at the next visit?
In Napiro, every client has a technical record: shades and shares, ratio, developer volume, processing time, result, with photos that stay private. The formula shows before the next appointment, without searching through a notebook. The trial lasts 14 days, no credit card.
Every client’s formula, found before she sits down.
