What this calculator does
Hair growth is commonly cited as averaging around 1 to 1.5 cm per month, though the actual rate varies from person to person, and by age, genetics and health. This calculator multiplies a chosen growth rate by a number of months to give a total, using 1.25 cm per month, the midpoint of that commonly cited range, as an editable starting point rather than a fixed number.
Because the real rate varies so much between individuals, the point of this tool is less about producing one precise figure and more about seeing how much a given rate adds up to over the length of time you have in mind, whether that is growing out a short cut or checking progress after a haircut.
The formula
Total growth is simply the number of months multiplied by the growth rate per month. The rate is also converted into a yearly figure and shown in both centimetres and inches.
| Term | Meaning |
|---|---|
| Growth rate | How much hair grows in a single month, in centimetres. The commonly cited average sits around 1 to 1.5 cm. |
| Months | The length of time being calculated over, which can include fractions such as 1.5 months. |
The inputs explained
| Field | What to enter |
|---|---|
| Number of months | The number of months you want to project growth over. |
| Growth rate per month (cm) | The monthly growth rate to use. The default of 1.25 cm is a commonly cited average; adjust it if you know your own rate tends to run faster or slower. |
When to use it
Growing out a haircut
Estimating how many centimetres will have grown back by a target date helps set expectations for how long a grow-out will realistically take.
Tracking a hair-health routine
Comparing an assumed average rate against what is actually measured over the same period is one rough way to see whether growth is tracking above or below typical.
Planning between salon visits
Working out expected length gained between now and a future appointment helps decide whether a trim or a bigger cut makes more sense.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How much does hair grow over different lengths of time?
Total growth at the default rate, across a range of common timeframes.
| Months | Total hair growth | In inches |
|---|---|---|
| 1 mo | 1.25 cm | 0.49 in |
| 3 mo | 3.75 cm | 1.48 in |
| 6 mo | 7.50 cm | 2.95 in |
| 9 mo | 11.25 cm | 4.43 in |
| 12 mo | 15.00 cm | 5.91 in |
| 24 mo | 30.00 cm | 11.81 in |
Questions
How much does hair grow in a month?
The commonly cited average is around 1 to 1.5 cm per month, which works out to roughly 12 to 18 cm a year. Individual rates vary with genetics, age, hormones and overall health, so treat it as a general guide rather than a personal guarantee.
Why is the growth rate editable instead of fixed?
Because hair growth genuinely differs between people, using one fixed number for everyone would be misleading. Entering your own observed rate, if you know it, gives a more accurate projection than the general average.
Does hair grow faster in summer?
Some studies suggest a small seasonal uptick in warmer months, but the effect is modest compared with the person-to-person variation in baseline rate, so this calculator treats the rate as constant over the period entered.
Can this account for hair breakage or trimming?
No, it calculates growth from the scalp only. Visible length gained can be less than the calculated growth if the ends are being trimmed or if breakage is occurring at the same time.
For counting the number of days or months between two specific dates, see the days until a date calculator.