SuddlTools

Beauty & hair

Hair developer calculator: which volume and how much?

Choosing between 10, 20, 30 and 40 volume developer is the step most home colorists get wrong. Tell us where your hair is now and where you want it, and we will suggest the volume and the exact amounts to mix.

Natural or current level. Compare with a level chart in daylight.
Sets a suggested amount of color below.
Check your product box. Most creams are 1:1, many lighteners 1:2.

What does hair developer do?

Developer is a cream form of hydrogen peroxide. When you mix it with hair color or bleach, it opens the hair cuticle so the color can get in, and it lightens your natural pigment. The volume number tells you how strong it is. Higher volume means more lift and faster processing, but also more potential for dryness, damage and scalp irritation.

Developer volumes explained

VolumePeroxideLiftBest for
10 volume3%Up to 1 levelGoing darker, toning, demi permanent color, refreshing the same shade
20 volume6%1 to 2 levelsStandard permanent color and gray coverage, gentle bleach on the scalp
30 volume9%2 to 3 levelsMore lift with color, bleach off the scalp such as balayage
40 volume12%3 to 4 levelsHigh lift color, professional use only, never bleach on the scalp

How to find your hair level

Hair levels run from 1, which is black, to 10, the lightest blonde. Check your roots in daylight against a level chart or the model photo on a box of color. Most people are darker than they think, especially if the ends are sun lightened. The number of levels between your starting point and your goal is what decides the developer.

How much color and developer do I need?

For a one to one ratio, mix equal parts: two ounces of color with two ounces of developer. For one to one and a half, use one and a half times as much developer, and for one to two, double it. Short or fine hair usually needs about two ounces of mixed product, shoulder length hair about four, and long or thick hair six to eight. The calculator suggests an amount when you pick your hair length, and you can change it to match your tube or bowl.

Mix only what you need. Once color and developer are mixed, they start reacting and can't be saved for later. If you run out halfway, mix a fresh small batch at the same ratio rather than stretching the old one.

Safety first

Do a skin allergy test 48 hours before every color, even with a brand you have used before, because sensitivity to hair dye can develop over time. Do a strand test on a hidden section to check the shade and condition. Work in a ventilated room, wear gloves, and never use hair dye on eyebrows or lashes. If you are going from very dark to very light, or your hair is already damaged, a professional colorist is the safest route.

Not sure which shade to choose? Take our skin undertone quiz and seasonal color analysis, then read our guide to the art and science of hair color.

Frequently asked questions

Can I use 20 volume developer instead of 30?
Yes. 20 volume lifts more slowly and less, but it is gentler. With bleach you can still reach your goal with 20 volume, it just takes longer or an extra session.
What happens if I use too much developer?
Too much developer dilutes the color, so it can come out lighter, patchy or with poor gray coverage, and it can dry the hair out. Stick to the ratio on your product.
Which developer is best for gray coverage?
20 volume is the standard for covering gray with permanent color, because it opens the resistant cuticle of gray hair so the pigment can take hold.
Can I put 40 volume developer on my scalp?
It isn't recommended. 40 volume can burn and irritate the scalp, and it is meant for professional high lift color and off scalp techniques.
Is this developer calculator free?
Yes, it is free and needs no sign up. It gives general guidance, so always follow the instructions on your product.