How much developer do you mix with hair dye?

In most hair color applications, colorists mix an equal amount of developer and color together. This formula is often referred to in parts or as a ratio. For example, the ratio 1 to 1 means to mix one part color with one part developer.

When colorists want to lighten hair by several shades, a service called high-lift color, they often add more developer to ensure maximum lift. A common formula used consists of one part color to two parts developer. Stylists rarely go over the 1 to 2 formula because adding too much developer changes the consistency of the hair color and doesn't offer any real advantages.