Hair Growth Calculator
Measured from your roots to your longest ends, hair pulled straight.
Roughly 12 in is shoulder, 14 in collarbone, 20 in mid-back on average height.
Most hair grows close to half an inch a month. Pick average unless you have measured your own.
A dusting is about a quarter inch. Anything over an inch is a proper cut, not a trim.
Everything is worked out in your browser. Nothing is sent to a server, saved, or shared.
Hair grows at a pace you cannot negotiate with. For most people it is close to half an inch a month, which works out at roughly six inches a year, and no product on a shelf changes that number by much. What you can change is how much of that growth you keep.
That is the gap the calculator above is built around. It subtracts what your trims take away from what your scalp produces, so the timeline you get is the real one rather than the optimistic one.
What the numbers actually mean
Three of the four inputs are straightforward. The one worth understanding is the trim schedule, because it is where most growing-out plans quietly fail.
What your scalp produces, measured at the root. Set mostly by genetics, age and general health. You have very little control here, and that is fine.
How much of that growth survives at the ends instead of breaking off or being cut away. This is where the control is, and where a long-hair plan is won or lost.
Someone growing half an inch a month and losing half an inch every four months to trims nets 4.5 inches a year. Someone with the same growth rate who trims a quarter inch twice a year nets 5.5. Same head of hair, a full inch of difference, decided entirely by scissors.
How long common goals actually take
These assume average growth of half an inch a month and a light quarterly trim, which is a realistic maintenance routine rather than a best case.
| Starting point | Goal | Realistic time |
|---|---|---|
| Pixie | Chin-length bob | About 10 to 12 months |
| Chin-length bob | Shoulder length | About 14 to 16 months |
| Shoulder | Collarbone | About 5 to 6 months |
| Collarbone | Mid-back | About 18 months to 2 years |
| Mid-back | Waist | About 12 to 15 months |
Two things shift these numbers in real life. Curly and coily hair grows at the same rate but shows far less of it, because a coil that measures eight inches stretched may sit at four. And damaged ends break faster than they grow, which is why some people feel stuck at one length for years.
What actually protects length
Nothing on this list makes hair grow faster. All of it stops growth disappearing at the ends, which produces the same result on the timeline.
Sleeping on silk or satin, or in a loose braid.
Detangling from the ends upward, on damp conditioned hair.
Heat protectant, and heat tools used at the lowest setting that works.
Regular conditioning, with extra attention to the last few inches.
Protective styles that keep ends tucked away rather than rubbing on collars.
Tight ponytails worn in the same spot every day.
Brushing soaking wet hair from the roots down.
Bleaching, then heat styling the same week.
Asking for a trim and accepting two inches because it looked neater.
Skipping conditioner on the ends because the roots feel greasy.
Most of what is sold as a growth product supports the hair you already have rather than speeding up the follicle. If you are short on a nutrient, correcting that can help, but taking extra when you are not deficient generally does nothing. Sudden shedding, bald patches or a widening part are worth taking to a doctor or dermatologist rather than a shelf, because those have causes a serum cannot reach.
Measure it properly, once a season
Checking your length every week is the fastest way to feel like nothing is happening, because half an inch a month is genuinely hard to see. Measure once every three months instead.
Dry, straightened hair. Wet hair stretches and curly hair coils, so measure the same way every time or the comparison is meaningless.
Pick one section and stick to it. The section just behind your ear is easiest to reach and does not vary the way a layered front does.
Photograph it against the same wall. A photo every three months shows progress that a tape measure argues about, especially with curls.
Frequently asked questions
Does trimming make hair grow faster?
No. Growth happens at the follicle and scissors never get near it. What trimming does is remove split ends before they travel up the strand and cause breakage higher than you wanted. That protects length, which looks like faster growth over a year even though the growth rate never changed.
How fast does hair grow in a month?
Around half an inch, or a little over a centimetre, for most adults. Some people run slightly faster and some slower, and the rate tends to slow gradually with age. If you have never measured your own, average is the safest setting in the calculator.
Why does my hair seem stuck at one length?
Usually because your ends are breaking at the same rate the roots are growing. It is a retention problem, not a growth problem. The other possibility is that you have reached your terminal length, which is the point where a hair reaches the end of its growth cycle and sheds naturally. Terminal length varies enormously between people.
Does curly hair grow more slowly?
It grows at the same rate, but it shows less of it. A coil that stretches to eight inches can sit at three or four, so months of progress are invisible. Curly and coily hair is also more fragile at the bends, so retention matters more here than anywhere else.
Do hair growth serums and supplements work?
Mostly they support the hair you already have rather than speeding up the follicle. Correcting a genuine nutritional deficiency can make a difference, but taking more of something you are not short of generally does not. If you are shedding heavily or seeing bald patches, that is a conversation for a doctor rather than a product.
How often should I trim if I am growing my hair out?
A quarter to half an inch every three to four months keeps ends healthy without eating your progress. Run both versions through the calculator above and you will see the difference over two years. The bigger risk is not the schedule but the chair: say the exact number out loud before the first cut.
Can I reach any length I want if I am patient enough?
Not quite. Every hair has a growth phase that lasts a set number of years before it sheds, and that length of phase is genetic. For some people it allows waist-length hair, for others it tops out around mid-back no matter how carefully they treat it. Retention gets you to your own maximum, not past it.
Are my numbers saved anywhere?
No. The calculator runs entirely in your browser. Nothing is sent to a server, stored, or shared, and your numbers disappear the moment you close the page.