Color & Developer Ratio
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.
The bottom line is you just want to use equal measure of hair color to developer to ensure best results.
©Hairfinder.com
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?