Hair Growth Rate Calculator

The Hair Growth Rate Calculator measures how fast your hair actually grows using two real measurements taken some weeks apart. Instead of assuming the population average of about 1.25 cm (0.5 inches) per month, you find your personal rate — then see how it compares to typical growth and how long your hair will be in the months ahead.

To use it, measure a section of hair (for example from a part down to the tip), wait a set number of weeks, and measure the same section again. Enter both measurements and the number of weeks between them. The calculator divides your length gain by the elapsed time to find your monthly and yearly growth rate, classifies it as slower, average, or faster than typical, and projects your length for the next year.

What Is a Normal Hair Growth Rate?

• Average: about 1–1.5 cm (0.4–0.6 inches) per month, or roughly 15 cm (6 inches) per year
• Slower: under ~1 cm (0.4 inches) per month
• Faster: over ~1.5 cm (0.6 inches) per month

Why Your Rate May Differ

• Genetics set the baseline pace and the length of your growth (anagen) phase.
• Age gradually slows growth, especially after your 30s.
• Nutrition — protein, iron, zinc, biotin, and vitamin D — fuels the follicle.
• Health and hormones, including thyroid function, influence the cycle.
• Breakage from heat, chemicals, or tight styles can make growth look slower than it is.

For the most accurate result, measure the same section under the same tension each time, and use a longer interval (8–12 weeks) to smooth out measurement error. This tool is a general guide and does not replace professional medical advice.