Hair Growth Calculator
Estimate how long it will take to grow your hair to a target length, accounting for the average growth rate and any regular trims.
How it works
Net rate = growth rate − trim rate · Months = (target − current) ÷ net rate
Scalp hair grows about half an inch (1.25 cm) a month on average, though genetics, age and health shift the rate. Regular trims to remove split ends subtract from your net gain, which is why hair that is never cut still gains length faster than hair trimmed often. The time to a target length is simply the length you need to gain divided by that net monthly rate.
Worked example
To go from 6 in to 12 in you need 6 more inches. Growing 0.5 in a month but trimming 0.125 in leaves a net 0.375 in per month, so it takes about 16 months — roughly a year and four months.
Frequently asked questions
How fast does hair really grow?
Scalp hair averages about 0.5 inch (1.25 cm) per month, or roughly 6 inches a year. Rates vary with genetics, age, hormones and health, and growth slows as each strand nears the end of its multi-year growth phase.
Do trims make hair grow faster?
No — trims do not speed growth at the root. But by removing split ends they prevent breakage that shortens hair, so healthy trims can help you retain length even though they slightly reduce net gain.
Can products make hair grow faster?
Most cannot meaningfully change the growth rate, which is set biologically. Good nutrition, scalp health and gentle handling mainly help by reducing breakage so more of what grows is kept.
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This calculator is for educational purposes. Double-check important results before acting on them.