Hair Growth Calculator
Calculate exactly how long it will take to grow your hair from its current length to your target. Factor in hair type, age, and health for a personalized growth timeline.
Your Hair Growth Timeline
Month-by-Month Timeline
Tips to Maximize Growth
A hair growth calculator is a free, browser-based tool that estimates how long it will take to reach a target hair length from your current length. It applies published average growth rates — about 0.5 inches (1.25 cm) per month — adjusted for hair type and age, and returns a month-by-month timeline instantly.
How Hair Growth Calculator Works
Calculate how long to grow your hair to any length. Enter current and target length, hair type, and get a personalized timeline. Enter your values into the form above and the calculator processes them instantly in your browser — no data is sent to any server.
How Fast Does Hair Grow
Human hair grows at an average rate of about 0.5 inches (1.25 cm) per month, or roughly 6 inches (15 cm) per year. However, this varies significantly based on genetics, ethnicity, age, health, and hair care practices. Asian hair tends to grow the fastest at up to 6.3 inches per year, while African-textured hair grows closer to 4 inches per year. The anagen (active growth) phase lasts 2-7 years, which determines your maximum possible hair length.
Factors That Affect Hair Growth Speed
Genetics and ethnicity: The single biggest factor. Your genes determine your growth rate, anagen phase length, and maximum hair length. Asian hair has the longest growth phase on average.
Age: Hair grows fastest between ages 15-30. After 30, growth gradually slows. After 50, it can slow to 0.25 inches per month or less due to reduced follicle activity.
Nutrition: Hair is made of keratin protein. Adequate protein intake, along with iron, zinc, biotin (B7), and vitamins A, C, D, and E are essential. Deficiencies directly slow growth.
Health and stress: Chronic stress triggers telogen effluvium (excessive shedding). Thyroid disorders, hormonal imbalances, and autoimmune conditions also impact growth. Good sleep and exercise promote healthy circulation to the scalp.
How to Speed Up Hair Growth
While you cannot exceed your genetic growth rate, you can ensure you are reaching your full potential. Eat a protein-rich diet with adequate iron and biotin. Consider a daily multivitamin or biotin supplement (2500-5000 mcg). Massage your scalp for 5 minutes daily to increase blood flow. Minimize heat styling, chemical treatments, and tight hairstyles that cause breakage. Use a silk or satin pillowcase to reduce friction. Trim split ends every 8-12 weeks — this does not speed growth but prevents breakage that makes hair appear to grow slower.
Hair Growth Calculator Accuracy
This calculator uses published scientific data on average hair growth rates by ethnicity, age group, and health factors. It provides an estimate based on population averages — your individual rate may be faster or slower. For the most accurate results, measure your hair growth over 2-3 months and compare to our estimates. If your hair seems to grow much slower than expected, consult a dermatologist to rule out underlying conditions.
What Dermatologists Say About Speeding Up Hair Growth
The honest answer is that no product, supplement or routine reliably makes hair grow faster than your genetic rate — what you can control is how much length you keep. The American Academy of Dermatology frames the goal as preventing breakage rather than accelerating growth, because hair that snaps mid-shaft never reaches the length your follicles actually produced. Two points are worth flagging against the popular advice. First, biotin supplements only measurably help people who are genuinely biotin-deficient, which is rare in anyone eating a normal diet; the AAD notes that high-dose biotin can also interfere with lab tests, including thyroid and cardiac blood work, so tell your doctor if you take it. Second, trimming does not change growth rate at the root — it removes split ends so they cannot travel up the shaft and cost you length later. For a clinical overview of the hair cycle itself, the NIH StatPearls chapter on hair growth physiology covers the anagen, catagen and telogen phases in detail. If shedding is sudden, patchy, or accompanied by scalp symptoms, that is a dermatologist visit, not a supplement problem. Last updated: 2026-08-28. Educational estimate only — not medical advice.
Frequently Asked Questions
How fast does hair grow per month?
On average, hair grows about 0.5 inches (1.25 cm) per month. Asian hair may grow up to 0.55 inches per month, while African-textured hair grows closer to 0.35 inches per month. Individual rates vary based on genetics, age, and health.
Does hair grow faster in summer?
Yes, slightly. Hair tends to grow about 10% faster in warm months due to increased blood circulation and hormonal changes. The difference is small — roughly 0.05 inches more per month — but it adds up over a season.
Can biotin supplements speed up hair growth?
Biotin (vitamin B7) supports hair growth, but supplements only help if you are deficient. For people with adequate biotin intake, supplements may not noticeably speed growth. The recommended dose is 2500-5000 mcg daily.
Does cutting hair make it grow faster?
No, this is a myth. Cutting hair does not affect the growth rate at the follicle. However, regular trims (every 8-12 weeks) prevent split ends from traveling up the shaft, which reduces breakage and helps you retain more length.
What is the maximum length hair can grow?
Maximum hair length is determined by your anagen (growth) phase, which lasts 2-7 years. At 6 inches per year with a 6-year anagen phase, the theoretical maximum is about 36 inches (3 feet). Most people have a 2-4 year anagen phase.
How accurate is this hair growth calculator?
This calculator uses published scientific averages for hair growth rates by ethnicity, age, and health. It provides a reasonable estimate, but individual variation is significant. Track your own growth over 2-3 months for the most accurate personal baseline.
How long does it take to grow hair 12 inches?
At the average rate of 0.5 inches per month, 12 inches takes about 24 months, or two years. Faster-growing hair at 0.6 inches per month reaches 12 inches in roughly 20 months, while slower growth at 0.35 inches per month needs closer to 34 months. Those figures assume you keep the length — breakage at the ends is what usually makes real-world progress slower than the arithmetic. Enter your own current and target length above for a personalised timeline.
Can anything actually make hair grow faster than your genetic rate?
No. Growth rate is set by your follicles and genetics, so no shampoo, oil, or supplement reliably exceeds it. The American Academy of Dermatology frames the realistic goal as retaining length rather than accelerating growth: protect against breakage, avoid tight styles and excessive heat, and treat any underlying scalp or thyroid condition. Biotin only helps people who are actually deficient, which is uncommon, and high doses can skew thyroid and cardiac lab results — mention it to your doctor if you supplement.
Is my data private?
Yes. All calculations run entirely in your browser. No data is sent to any server or stored anywhere.