Hair Growth Calculator

Frequently Asked Questions

How fast does hair actually grow?

The average is about 1.25 cm (0.5 inches) per month, or about 15 cm (6 inches) per year. Individual rates range from roughly 0.6 to 1.5 cm per month. Asian hair tends to grow slightly faster on average; African hair slightly slower, though with more variation among individuals than between groups.

Does cutting hair make it grow faster?

No. Hair grows from the follicle at the scalp and cutting the ends has no effect on growth rate. Trimming helps by preventing splits from travelling up the shaft and causing breakage, which improves length retention rather than speed.

Do hair growth supplements work?

Biotin supplements are widely marketed but only help if you have an actual biotin deficiency, which is uncommon in people eating a varied diet. Iron, vitamin D, and zinc deficiencies are more commonly linked to hair loss and may help when corrected. Consult a doctor before supplementing; some hair supplements include doses well above safe upper limits.

How do I measure my hair length?

For a consistent measure, use a soft tape measure or ruler against a flat section of hair pulled straight down at the back or side of your head. Measure from the scalp (or from where you part) to the ends of the majority of your hair, not the longest single strand.

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Estimates for informational purposes only.

Important Disclaimer: Estimates for informational purposes only.

This calculator provides estimates for informational purposes only. Results are based on assumptions and may not reflect actual outcomes. Consult qualified professionals in relevant fields before making important decisions based on these results.

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How This Calculator Works

Enter your current hair length, your target length, and your estimated monthly growth rate. The calculator divides the length difference by the monthly rate to give you the number of months and years needed. You can also account for regular trims: if you trim 0.5 cm every 8 weeks, the calculator subtracts that from net monthly growth. Average human hair grows about 1.25 cm (0.5 inches) per month, but individual rates range from 0.6 cm to over 1.5 cm depending on genetics, health, nutrition, and age.

What Affects Hair Growth Rate

Genetics: The single biggest factor. Your maximum terminal length and growth rate are largely determined by your genetic makeup.

Age: Growth rate peaks in the 20s-30s and tends to slow slightly with age.

Nutrition: Protein, iron, zinc, biotin, and vitamins D and B12 support hair growth. Deficiencies can cause shedding and slow growth.

Hormones: Thyroid issues, PCOS, and post-partum hormonal changes frequently cause significant hair shedding and altered growth cycles.

Scalp health: Dandruff, product buildup, and scalp inflammation can slow growth and contribute to breakage.

Stress: Telogen effluvium (stress-induced shedding) can temporarily increase hair loss by pushing follicles into the resting phase.

The Hair Growth Cycle

Hair grows in three phases. Anagen (active growth): lasts 2-7 years and determines maximum hair length - longer anagen means potentially longer hair. Catagen (transition): 2-3 weeks, the follicle shrinks and growth stops. Telogen (resting/shedding): 3-4 months, the old hair is held in the follicle before a new hair pushes it out. At any time, about 85-90% of your hair is in anagen, 1-2% in catagen, and 10-15% in telogen. Losing 50-100 hairs per day is completely normal and part of this cycle.

Trimming vs. Growth: The Truth

Hair grows from the scalp, not the ends, so trimming does not directly speed up growth. However, trimming does indirectly support length retention by removing split ends before they travel up the hair shaft and cause breakage. If your hair breaks off at the same rate it grows, you will see no net length increase. Regular small trims (0.5-1 cm every 8-12 weeks) are often more length-retaining than letting ends split for months and then requiring a larger cut. The real growth bottleneck is breakage and retention, not follicle speed.

Tips to Maximise Length Retention

If your goal is maximum length, length retention matters as much as growth rate. Reduce heat tool use or use heat protectant every time. Sleep on a satin or silk pillowcase or use a satin bonnet to reduce friction breakage. Deep condition regularly to maintain elasticity. Detangle gently with a wide-tooth comb or your fingers on wet conditioned hair, not dry hair. Protective styles (braids, buns, twists) reduce daily mechanical stress on the ends, which is where most length is lost to breakage.

Hair Growth Calculator

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