The simplest way to measure hair growth is with a flexible tape measure, tracking length from your hairline to the tips of your longest strands at regular intervals. Hair grows between 0.2 and 0.7 inches per month on average, so you’ll need at least four to six weeks between measurements to see a reliable difference. Beyond simple length, there are several ways to track growth depending on whether you’re monitoring progress after a haircut, evaluating a treatment, or checking for thinning.
What Counts as Normal Growth
Scalp hair grows roughly 0.5 to 1.7 centimeters per month, which works out to about 2 to 7 inches per year. That range is wide because growth rate varies by genetics, age, and even the time of year. A study tracking 14 men over 18 months in the UK found that the proportion of actively growing scalp follicles peaked at over 90% in March and dropped to its lowest point in September. Shedding followed the opposite pattern, peaking around August and September at about 60 hairs per day, more than double the winter rate.
Your hair’s maximum possible length is determined by how long each follicle stays in its active growth phase, called anagen. For scalp hair, anagen lasts two to eight years. Once a follicle shifts out of this phase, the strand stops lengthening and eventually sheds. This is why some people can grow hair to their waist while others plateau at shoulder length, even without trimming. Anagen duration also shortens with age, which is one reason hair tends to get finer and shorter over time.
Measuring Length at Home
A soft fabric tape measure is the most practical tool. Place one end at your front hairline and run the tape over the crown of your head, following the curve of your scalp down to the tips of your longest strands. For curly or coily hair, gently straighten a section before measuring, since shrinkage can hide several inches of actual length.
Body landmarks give you a quick visual reference without a tape measure:
- Ear to chin: roughly 8 to 10 inches
- Shoulder to armpit: roughly 12 to 14 inches
- Mid-back to waist: roughly 16 to 20 inches
- Below the waist to hips: 22 to 26+ inches
These landmarks are useful for setting goals and recognizing progress over months rather than weeks. Checking against the same landmark every time removes guesswork about whether your hair has actually grown or just looks different on a given day.
Tips for Consistent Readings
Measure the same section of hair each time, ideally a strand near the crown where growth tends to be most representative. Wet hair or freshly washed hair can stretch slightly, so pick one condition and stick with it. Record your measurement with the date. Because monthly growth can be as little as a fifth of an inch, measuring more often than once a month usually just introduces measurement error that masks real progress.
Tracking Density and Thickness
Length alone doesn’t tell the full story if your concern is thinning. Hair density (how many strands per square centimeter) and hair diameter both matter for how full your hair looks. Dermatologists assess these with a tool called a trichoscope, essentially a magnifying camera pressed against the scalp. It reveals details invisible to the naked eye: the ratio of thick terminal hairs to fine wispy ones, how many hairs emerge from each follicle, and signs of inflammation or scarring around the follicle openings.
A more detailed clinical method, the phototrichogram, involves trimming a small patch of hair to half a millimeter, waiting two days, then photographing the regrowth. Software color-codes each hair by phase: actively growing, resting, or at the end of its cycle. The whole process takes about 20 minutes and gives an objective snapshot of how much of your hair is actually in the growth phase versus preparing to shed. You can’t replicate this at home, but it’s worth knowing about if a dermatologist suggests it.
Using Photos to Track Progress
Consistent photography is one of the most reliable at-home methods for catching gradual changes in hair growth. The key word is consistent. Take photos from the same angles (front, top, both sides), in the same lighting, at the same distance from the camera. Even small differences in lighting or angle can make hair look thicker or thinner than it actually is.
Several smartphone apps now automate this process. Apps like HairSnap and Hairly guide you through capturing standardized photos and then generate side-by-side comparisons filtered by angle. Some use image analysis to estimate hair density and flag changes in coverage over time, presenting results as heatmaps, charts, or before-and-after sliders. These tools work best for tracking density changes rather than length, and they’re most useful when you photograph on a regular schedule, such as every two to four weeks.
The Hair Pull Test for Shedding
If you’re worried about losing more hair than normal, there’s a simple test you can try. Grasp a group of about 50 to 60 hairs between your thumb and first two fingers, then pull gently but firmly from the scalp outward to the tips. If more than five or six hairs come out easily, that suggests active hair loss beyond typical daily shedding. Repeat this in several areas of your scalp, since some conditions cause patchy loss while others are diffuse.
For accurate results, avoid washing your hair for at least 24 hours before the test. Freshly washed hair has already shed its loosest strands in the shower, which can make the test falsely reassuring. This isn’t a diagnosis on its own, but a positive pull test in multiple areas is a useful data point to bring to a dermatologist.
When Growth Slows Down
A noticeable slowdown in hair growth sometimes traces back to nutritional gaps. Iron deficiency and low thyroid function are among the most common culprits, and both are detectable through blood work. Biotin deficiency gets a lot of attention in supplement marketing, but the evidence for biotin helping hair growth exists only in people who are actually deficient. A review of the research found 18 cases where biotin supplementation improved hair growth, and every single one involved a patient with a confirmed deficiency from a specific cause: a restricted diet, pregnancy, alcoholism, anticonvulsant medications, long-term antibiotic use, or a genetic condition. In one case, an infant on a specialized formula regrew hair after two months of supplementation. For people with normal biotin levels, there’s no evidence that extra biotin speeds up growth.
Excessive consumption of raw eggs is one documented dietary cause of biotin deficiency, since a protein in raw egg whites binds biotin and prevents absorption. Cooked eggs don’t have this effect.
Putting It All Together
For most people tracking hair growth at home, the combination of monthly tape measurements and consistent photos covers everything you need. Measure from the same spot, photograph in the same conditions, and log dates. Expect about half an inch of growth per month as a baseline. If you’re seeing significantly less than that over several months, or if the pull test consistently yields more than five or six hairs, those are signals worth investigating with a dermatologist who can use clinical tools like trichoscopy to see what’s happening at the follicle level.