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Hair growth calculator icon showing flowing hair

Hair Growth Calculator

Hair Growth Calculator

Predict your hair length or time to your goal

Saved Calculations
No history yet. Calculate below to start tracking.

On average, scalp hair grows about 0.5 inches (1.27 cm) per month. Genetics, age, sex, nutrition and stress can push individual rates faster or slower, which is why a speed adjustment is included below.

Growth isn't perfectly linear for everyone since hair cycles through active (anagen), transitional (catagen) and resting (telogen) phases — but the average rate is a solid planning estimate over weeks or months.

What Do You Want to Know?
Current Length
Time Period
Growth Speed
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👥 Your Result
Predicted Length
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Fill in the fields above to calculate
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Length Gained
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Effective Rate / Month
Calculation
Estimate only — individual growth varies with genetics, health, hair care and hormonal changes.

Whether you’re growing your hair out for a specific length goal or just curious how long it’ll be by a certain date, this calculator projects hair growth in either direction using the well-established average scalp hair growth rate.

How to use this hair growth calculator

  1. Choose what you want to know: your hair length after a time period, or the time to reach a target length.
  2. Enter your Current Length.
  3. Enter either your Time Period, or your Target Length, depending on the mode.
  4. Select your Growth Speed: slower, average, or faster than typical.
  5. Read your Predicted Length (or Time to Reach Target), Length Gained, and Effective Rate per Month.

What this calculator does

On average, scalp hair grows about 0.5 inches (1.27 cm) per month. This calculator applies that baseline rate, adjusted by your selected growth speed multiplier, to project either your future length after a given time period, or how long it will take to reach a target length from where you are now.

Predicted Length = Current Length + (Growth Rate per Month × Speed Multiplier × Months)
Time to Target = (Target Length − Current Length) ÷ (Growth Rate per Month × Speed Multiplier)

Why individual growth rates vary

Genetics, age, sex, nutrition, and stress can all push an individual’s actual hair growth rate faster or slower than the population average, which is why this calculator includes a speed adjustment (slower, average, or faster than average) rather than assuming everyone grows hair at an identical rate.

Why growth isn’t perfectly linear for everyone

Hair doesn’t grow at a perfectly constant rate for every strand simultaneously, it cycles through active (anagen), transitional (catagen), and resting (telogen) phases, with different hairs on your head at different phases at any given time. Despite this underlying complexity, the average growth rate remains a solid planning estimate over periods of weeks or months, even if it’s not a precise guarantee for any single strand.

Frequently asked questions

What’s the average rate hair grows?

About 0.5 inches (1.27 cm) per month for scalp hair, though individual rates vary with genetics, age, nutrition, and other factors.

Why might my hair grow faster or slower than the average?

Genetics, age, sex, nutrition, and stress levels can all influence individual hair growth rate. This calculator’s Growth Speed setting lets you adjust the estimate to better match your own observed rate rather than using a flat average for everyone.