Home / Tools / Hair Length Calculator
Hair Length Calculator
Enter your current and desired hair length to estimate how long it will take to grow it out, based on an adjustable average monthly growth rate.
Estimated Growth
Hair growth varies between individuals based on genetics, health, hair care routine and other factors. This calculator provides a general estimate and should not be considered medical advice.
How Hair Growth Actually Works
Hair grows from follicles in the scalp in a repeating cycle: an active growth phase that can last several years, followed by a brief transitional phase, and then a resting phase before the strand eventually sheds and a new one begins growing in its place. At any given time, the vast majority of your hair follicles are in the active growth phase, which is why hair generally grows at a fairly steady, predictable rate over the course of months — even though the exact rate varies from person to person.
Why the Default Rate Might Not Match You
Half an inch per month is a commonly cited average, but it's exactly that — an average, not a universal constant. Genetics play the largest role in your personal growth rate, but age, overall health, nutrition, and hormonal factors all contribute too. Hair growth also tends to slow slightly with age, and can be temporarily affected by significant stress, illness, or rapid changes in diet. If you've tracked your own hair growth over a few months with photos or measurements, use that number instead of the default — it will give you a far more accurate estimate than a generic average.
Why "Grown Length" Isn't Always What You See
One common source of frustration: hair can be growing at a completely normal rate while still not appearing to get any longer, because breakage at the ends is happening at roughly the same pace as new growth. If your hair doesn't seem to be gaining length despite months of growth, the more likely culprit is often breakage — from heat styling, chemical processing, or friction — rather than a slow growth rate. Addressing breakage (see our guide on caring for dry hair) often does more for visible length than trying to speed up growth itself, which is largely determined by genetics and not easily changed by products.
Planning Around a Growing-Out Period
This calculator is especially useful if you're growing out a shorter cut, an undercut, or bangs and want a realistic sense of when you'll hit a length you're happy with — and, just as importantly, when to schedule shaping trims along the way so the in-between stages look intentional rather than awkward. Bring your target timeline into your next salon visit and ask your stylist how they'd recommend trimming through the growing-out process.
A Note on Supplements and "Growth" Products
Plenty of products claim to speed up hair growth, but the underlying rate hair grows from the follicle is largely determined by genetics and overall health, not topical products. Some supplements may help if you have an actual nutritional deficiency contributing to slower growth or shedding, but that's a question for a doctor, not a marketing claim on a bottle. Use this calculator with your natural rate — adjusted honestly based on your own tracked history — rather than an optimistic number from a product label.