How Long Growing Out Gray Hair Takes, by Hair Length

Growing out gray hair takes 2 to 3 months for every inch of dyed hair. That is because scalp hair grows 4 to 6 inches a year, according to Cleveland Clinic. With 2 inches of dyed hair, the wait is 4 to 6 months. With 12 inches, it is 2 to 3 years, unless you cut some of it off.

This post is part of our guide to caring for gray hair. Below is the math, a table by length, and the ways people shorten the wait.

How fast hair grows

Cleveland Clinic gives the growth rate two ways. An article on hair growth says hair grows 4 to 6 inches a year, which is 10.2 to 15.2 centimeters. Its page on the hair follicle says hair grows about 1 centimeter a month.

Studies of single hairs give similar numbers. A 2004 study in the European Journal of Dermatology measured 3,343 scalp hairs from women. Pigmented hairs grew 0.35 millimeters a day and white hairs 0.38 millimeters a day. Over 30 days, that is 10.5 and 11.4 millimeters. In that study, the slower growth that often comes with age affected only the pigmented hairs, not the white ones.

Growth also differs between people. A 2016 study of 2,249 young adults from 24 ethnic groups found that hair growth varied with scalp area, sex and geographic origin. On average, African hair grew more slowly in that study and Asian hair faster.

The timeline by length

The table shows how long new gray hair takes to reach a given length at the Cleveland Clinic rate. At 6 inches a year, each inch takes 2 months. At 4 inches a year, each inch takes 3 months.

Dyed length to replace	At 6 inches a year	At 4 inches a year
2 inches (5.1 cm)	4 months	6 months
4 inches (10.2 cm)	8 months	12 months
6 inches (15.2 cm)	12 months	18 months
8 inches (20.3 cm)	16 months	24 months
12 inches (30.5 cm)	24 months	36 months

Two things to keep in mind when you read it:

• It is the time for new gray to reach that length. You still need to cut off the dyed ends at some point. If you keep the same length, your last cut removes the last of the color.
• Your rate may differ. The range above is for scalp hair in general. Measure your own roots a month after your last color to find your own rate.

To measure, use a ruler at the part. If you see half an inch of gray after one month, you are near the fast end of the range. If you see a third of an inch, you are near the slow end.

Why the first months feel slow

The root line shows up almost at once. A 2015 review in the International Journal of Trichology explains that the white roots seen 10 to 15 days after permanent color are new growth, not dye washing out. The same review says the roots of permanent color need a touch-up after 15 to 30 days. When you stop, the line keeps moving away from the scalp, and in the first months it is easy to see.

Growth also is not perfectly even. Cleveland Clinic says about 80 percent of your hair is actively growing at any time. The American Academy of Dermatology (AAD) describes the rest of the cycle: a hair may be resting without getting any longer, or falling out. So some roots grow out more slowly than others.

Ways to shorten the wait

There is no quick way to make hair grow faster. A Cleveland Clinic article on hair growth says there is no miracle cure for that. What you can change is how much dyed hair you keep.

• Cut shorter. This is the only sure way to finish sooner. Every inch you cut is 2 to 3 months you do not have to wait.
• Trim often. Regular trims remove the oldest dyed ends a little at a time. They let you keep more length, but the process takes longer.
• Blend the line. Highlights or lowlights can make the line between gray and dyed hair less sharp. Our guide to gray blending and lowlights explains how.
• Use color that fades. The 2015 review says demi-permanent color fades after 10 to 15 shampoos or sooner, so the contrast softens as it fades.
• Cover roots for events. Sprays and powders can hide the line for a short time. See root touch-up products.

Plan the whole change

A plan helps. Decide how short you are willing to go and when. Book trims at regular intervals. The new gray may feel different from your dyed ends; our page on why gray hair feels different explains what the research says about texture. Our page on growing out gray hair walks through each stage, and styling gray hair covers cuts and products for the months in between. For our editors' view on cuts, read haircuts that work with gray hair.

If your graying is sudden or patchy, or comes with other symptoms, see a doctor before you plan anything. The AAD notes that an underlying condition, such as a vitamin deficiency, can affect hair color.

LIUMIQ is working on a gradual color product for gray hair. It is not available to buy. You can join the waitlist to hear how the work progresses.