Color & Developer Ratio

Hair color and developer
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Q: What is the ratio of color to cream developer? 1 to 1 means 1 oz. or what?
A: When mixing color formula with a developer (whether a cream developer or liquid) the ratio of 1:1 means that you combine equal parts.
Depending on how much you need, that could mean you combine 2 ounces of color with two ounces of developer (2 ounces is the standard size bottle for most hair color formulas) or one gallon of color and one gallon of developer. (You would never need so much color at one time unless you are working in an industrial setting, such as wig making.)
The bottom line is you just want to use equal measure of hair color to developer to ensure best results.
See also:
How to dye your hair
What does the hair color developer do?
Can most developers be used with other products?
Is there a difference between hair developer and hair activator?