Hair Growth Calculator
Estimate how long hair takes to reach a target length. Enter current length and goal length in inches or centimeters and pick a growth pace to see the months and years to get there at average scalp rates.
Example: with Current length 8 · Target length 18 · Unit inches · Growth pace Average (~0.5 in/month) → Time to reach goal: 20 months (~1.7 years).
- Length to grow10 in to grow
- Pace used0.5 in/month (6 in/year)
- NoteAverage scalp growth ≈ 0.5 in (1.25 cm) per month (AAD); your rate varies.
Computed by the calculator below using its default values. Change any input to see your own numbers.
Scalp hair grows about half an inch (1.25 cm) a month on average per the American Academy of Dermatology, but genetics, age, and health shift individual rates.
What to expect month to month
Hair grows from the follicle at a fairly steady pace — the American Academy of Dermatology cites roughly half an inch, about 1.25 cm, per month, or six inches a year. So going from a bob at 8 inches to shoulder-blade length at 18 inches is about 10 inches, or roughly 20 months at the average rate. Slower growers might see closer to a third of an inch a month, stretching the same goal past two and a half years.
The number is only part of the story. At any moment about 85–90% of your hairs are actively growing and the rest are resting, and breakage at the ends can quietly offset new growth at the roots. Trims, heat, and handling affect the length you keep even when the follicle keeps producing on schedule.
How it’s calculated
Months = (target − current) ÷ monthly rate. Rates: slow 0.3 in, average 0.5 in, fast 0.6 in per month; in centimeters these are multiplied by 2.54 (0.76, 1.27, 1.52 cm). Years = months ÷ 12.
Uses a constant average rate; real growth varies with genetics, age, hormones, and nutrition, and only about 85–90% of hairs grow at once while breakage can reduce retained length. Not medical advice.
Growth at the average rate
| Timeframe | Inches | Centimeters |
|---|---|---|
| 1 month | 0.5 in | 1.3 cm |
| 3 months | 1.5 in | 3.8 cm |
| 6 months | 3 in | 7.6 cm |
| 1 year | 6 in | 15.2 cm |
| 2 years | 12 in | 30 cm |
American Academy of Dermatology: scalp hair grows ~0.5 in (1.25 cm) per month; individual rates vary.
Common mistakes
- Expecting your ends to keep every inch grown — breakage offsets root growth.
- Assuming a product can dramatically speed the follicle; rate is mostly set by genetics and health.
- Mixing inches and centimeters between the two boxes.
- Treating the estimate as exact — growth pace differs person to person and over a lifetime.
Frequently asked questions
How fast does hair grow?
On average about half an inch (1.25 cm) per month, or roughly six inches a year, according to the American Academy of Dermatology. Individual rates run a bit slower or faster.
How long to grow hair from short to long?
Divide the length you need by the monthly rate. From 8 to 18 inches is 10 inches, about 20 months at the average half-inch-per-month pace.
Can I make my hair grow faster?
You can protect length by limiting breakage, heat, and tight styles, and by eating well, but the follicle's base rate is mostly genetic. Dramatic speed-ups are unlikely.
When should sudden hair changes see a professional?
New shedding, thinning, or patchy loss can signal a medical issue. A dermatologist can evaluate it rather than a growth estimate.