Hair Growth Calculator

Estimate how many months it will take to reach a target hair length, and see your projected target date, using the standard average scalp growth rate.

Quick Facts

Average growth rate
≈0.5 in (1.25 cm) per month
About 6 in (15 cm) per year; individual rates commonly range roughly 0.3–0.7 in/month with genetics, age, and health.

Your Results

Calculated
Time to goal length
-
Months (and weeks) needed
Estimated target date
-
If growth stays steady
Net growth rate
-
Growth rate minus trim loss
Length in 6 months
-
Projected at net rate

Ready

Enter your current length, goal length, and growth rate, then press Calculate.

About the Hair Growth Calculator

This calculator estimates how long it will take to grow your hair from its current length to a goal length, using the standard, widely cited average scalp hair growth rate of about 0.5 inch (1.25 cm) per month — roughly 6 inches (15 cm) per year. It also accounts for regular trims, since a trim removes length even while new hair is growing in underneath.

The formula

The math is a simple rate calculation:

  • Net growth rate = growth rate − trim loss (inches per month)
  • Length needed = goal length − current length (inches)
  • Months to goal = length needed ÷ net growth rate
  • Projected length at N months = current length + (net growth rate × N)

For example, growing from 6 inches to 12 inches at the average rate of 0.5 in/month with no trims takes (12 − 6) ÷ 0.5 = 12 months. If you also trim 0.25 in/month to keep ends healthy, your net rate drops to 0.25 in/month, and the same 6-inch gain now takes 24 months.

How to get the best results

  • Measure current and goal length the same way (pulled straight, from scalp to tip) so the difference is accurate.
  • Use 0.5 in/month as a reasonable default, but adjust it if you know your own rate tends to run faster or slower.
  • Set trim loss to 0 if you don't get regular trims; otherwise use the length you typically have removed each visit, converted to a monthly average.

Practical context

This is a linear estimate based on an average rate — real hair growth is not perfectly constant and can be affected by season, stress, hormones, diet, and hair health, and growth also naturally slows or stops for individual strands during the shedding phase of the hair cycle. Treat the result as a planning estimate, not a guarantee, and re-check your measured length periodically to keep the estimate on track.

Frequently Asked Questions

How fast does hair actually grow?
The commonly cited dermatological average is about 0.5 inch (1.25 cm) per month, or roughly 6 inches (15 cm) per year. This is an average across the scalp — individual rates typically range from about 0.3 to 0.7 inch per month depending on genetics, age, hormones, nutrition, and overall health.
How does the calculator work out the target date?
It divides the difference between your goal length and current length by your net monthly growth rate (growth rate minus any regular trim loss), then adds that many months to today's date: months to goal = (goal length − current length) ÷ (growth rate − trim loss).
Why do I need to enter a trim loss value?
Regular trims remove length even as new hair grows in, so your net length gain is growth rate minus trim loss. If you trim 0.25 inch every month and grow 0.5 inch, your hair only lengthens by a net 0.25 inch per month. Leave trim loss at 0 if you don't trim on a fixed schedule.
Can hair grow faster than average with supplements or products?
Growth rate is largely determined by genetics and follicle biology, and most healthy people already grow hair near the average rate. Correcting an actual nutritional deficiency can restore normal growth, but there is no well-established way to reliably push growth rates far above the typical 0.5 inch per month for someone who is already healthy.

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