Hair Growth Calculator
Enter your current hair length and the length you want. The calculator estimates how many months that takes at an average growth rate of about 1 cm (0.4 inch) a month, with a slower and a faster figure, and takes planned trims into account.
Free, no sign-up. What you enter stays in your browser: it is not saved or sent to HerFound. Reviewed .
Units
Measure from the root to the tip. Stretch wavy, curly or coily hair straight to measure it.
Enter your current length and your goal length to see how long it may take.
This is general information, not medical advice. It cannot take your own health history into account. For anything that worries you, speak to a doctor, midwife or pharmacist.
How it works
The sum is: months = (goal length - current length) / growth per month. The average used is 1 cm a month, which is about 0.4 inch a month or 12 cm (4.7 inches) a year. A medical review of hair and scalp conditions gives scalp hair growth as about 0.3 mm a day, or 1 cm a month. You will often see half an inch a month quoted; the sources we read give a slightly lower figure.
The range uses 0.8 cm a month for slower growth and 1.2 cm a month for faster growth. These come from a published study that measured growth in two groups of young adults: the averages were 0.256 mm a day in volunteers from central and western Africa and 0.396 mm a day in white European volunteers, which is 0.8 and 1.2 cm a month. Individual people in that study ranged from 0.15 to 0.36 mm a day within one group, so your own rate can sit anywhere in or outside this range whatever your hair type.
Trims are spread evenly over time. Trim per month = amount cut each time x 30.44 / (7 x weeks between trims). Net growth = growth per month - trim per month. If you cut 1 cm every 12 weeks, that is 0.36 cm a month, so average net growth is 0.64 cm a month. If trims remove as much as grows, the calculator says the goal will not be reached.
The date is today plus the number of months x 30.44 days. A month is counted as 30.44 days, the average over a year.
What it cannot tell you
- Your growth rate is set mostly by your genes and changes with age. The calculator cannot measure it. To find your own rate, measure the same section of hair on the same day each month for three months.
- It counts growth at the root, not length kept. If hair breaks at the ends as fast as it grows, it can seem not to grow at all. Each hair also grows for a limited time, about 2 to 6 years, before it is shed, which sets a limit on length that differs between people.
- It assumes nothing about products. None of the sources used here report a shampoo, oil or supplement that makes healthy hair grow faster than its natural rate.
- It is not a check on hair loss. Losing 50 to 100 hairs a day is normal. See a doctor if you are worried about hair loss, for example sudden shedding or bald patches.
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Common questions
Scalp hair grows about 1 cm (0.4 inch) a month on average, which is about 0.3 mm a day. The rate differs between people. In one published study, group averages ranged from about 0.8 cm to 1.2 cm a month.
Growing hair 6 inches (about 15 cm) takes around 15 months at the average rate of 1 cm a month. At a slower rate of 0.8 cm a month it takes about 19 months, and at a faster rate of 1.2 cm a month about 13 months. Regular trims add to that time.
No, trims do not make hair grow faster. Hair grows from the follicle in the scalp, and cutting the ends does not change that. A trim removes length, so this calculator subtracts planned trims from growth.
Growth rate does vary between people, and published studies have found differences between group averages. One study measured an average of 0.256 mm a day in African volunteers and 0.396 mm a day in white European volunteers, with a wide spread between individuals. Curly and coily hair also looks shorter than it is because it shrinks as it dries, so measure it stretched.
Hair that seems to stop growing is usually still growing at the root but breaking at the ends, or it has reached the length its growth phase allows. Each scalp hair grows for about 2 to 6 years before it falls out. If you also notice sudden shedding or bald patches, see a doctor.