How to use the hair developer calculator
- Choose color or bleach. Pick hair color to deposit or lift a little, or lightener (bleach) for bigger lifts.
- Enter your current and target level. Use the 1 to 10 level scale, where 1 is black and 10 is the lightest blonde.
- Tick gray coverage if needed. Gray hair often needs 20 volume to open the cuticle for even coverage.
- Set the amount and ratio. Pick your hair length or enter the amount of color, and the mixing ratio from your product box.
- Mix and follow the safety notes. See the developer volume, exact amounts of color and developer, and timing and patch test advice.
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
| Volume | Peroxide | Lift | Best for |
|---|---|---|---|
| 10 volume | 3% | Up to 1 level | Going darker, toning, demi permanent color, refreshing the same shade |
| 20 volume | 6% | 1 to 2 levels | Standard permanent color and gray coverage, gentle bleach on the scalp |
| 30 volume | 9% | 2 to 3 levels | More lift with color, bleach off the scalp such as balayage |
| 40 volume | 12% | 3 to 4 levels | High lift color, professional use only, never bleach on the scalp |
Worked example
You have level 5 light brown hair and want level 7 dark blonde, with no gray. That is 2 levels of lift, which 20 volume handles gently. For shoulder length hair you might use 2 oz of permanent color, and at a 1:1 ratio you mix it with 2 oz of 20 volume developer, 4 oz in total. If you were bleaching instead at a 1:2 ratio, 1 oz of lightener would need 2 oz of developer.
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.
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.
