Hair Dye Amount Calculator

How the hair dye amount is worked out

The amount of hair color you need depends on how much hair there is to saturate, not on the shade. The calculator starts from how much mixed product (color plus developer) a full head takes, adjusts it for density, application and porosity, then turns it into whole boxes or tubes. Every number is a rule of thumb that colorists use as a starting point — it is not a measurement of your hair.

full head  = base amount for your length × density factor
roots      = 50 ml × density factor (never more than a full head)
ends       = full head × 0.75
porous     = amount × 1.2
boxes      = mixed amount ÷ 120 ml, rounded up
tubes      = (mixed ÷ (1 + developer parts)) ÷ 60 ml, rounded up

The base amounts

A full head of medium-density hair takes roughly 60 ml of mixed color when short, 120 ml at shoulder length, 180 ml from armpit to bra-strap length and 240 ml from mid-back down. Fine hair uses about 80% of that and thick or very coily hair about 130%, because every strand has to be fully coated for even color. Very porous hair and resistant gray soak up more, so ticking that box adds about 20%.

Box kits and professional tubes

A typical box kit makes about 4 fl oz (120 ml) once mixed. A professional tube holds about 2 oz (60 ml) of color, which you mix with developer at the ratio your color line gives — 1:1, 1:1.5 or 1:2. At 1:2, one tube makes 180 ml of mixed color. For developer strength and exact mixing amounts, use the developer mixing calculator.

When to buy one extra

The result suggests a spare when you would use more than 85 percent of what you buy, when your hair is thick or very long, when it is very porous or resistant gray, or when you are doing a full head yourself. Running out halfway is the most common cause of patchy home color.

What this cannot tell you

It cannot tell whether a shade will show on your hair, how long to process, or whether your hair is ready for color. Do a patch test before every use and a strand test for any new shade, and follow the manufacturer's directions. For lightening, big color changes or relaxed hair, see a licensed colorist. To see how many levels a new shade has to lift, check the hair color level chart.