How we test
Every score on this site comes from criteria we publish before we use them. Here they are.
What a score is
A testing score is our judgement of a product we physically handled, on a scale of 1 to 10. It is not a measure of evidence. Our evidence scale grades research; this grades hardware. A device can score 9 for build quality and still have almost no evidence that it regrows hair, and we will say both.
The overall mark is a weighted average of the criteria below. Weights are published with the criteria, so you can see which columns moved a number.
No test, no score
We only score products we have used. If a product appears on this site without a score, it is because we have not handled it, and we say so rather than quietly ranking it anyway. A roundup pick always traces back to a test record with a named tester and a date.
How we get the units
- Purchased
- We bought this unit ourselves at full price.
- Gifted by the brand
- The brand sent us this unit free of charge. We kept it, and nobody reviewed this write-up before publication.
- Loaned by the brand
- The brand loaned us this unit and we returned it. Nobody reviewed this write-up before publication.
Which of those applies is shown next to every score. Accepting a free unit does not buy a good review, and a brand never sees a write-up before it is published.
Re-testing
Hardware gets revised and formulas get changed without the name on the box changing. We flag a product for a fresh look after 18 months, and every score shows the date it was earned.
Affiliate links
Reviews and roundups carry affiliate links, and every one of those pages says so above the first link. Commissions do not depend on what we score a product, and no brand can pay for a place in a roundup. See our editorial independence policy.
The criteria, by product type
Criteria are per product type, not one list for everything: battery life is meaningless for a manual brush, and bristle softness is meaningless for a laser cap.
Manual scalp massager (Scalp tools)
6 criteria, weights total 13
- Scalp feel
- weight 3 of 13 How the tips feel in use: firm enough to be worth doing, blunt enough not to scratch. Judged over at least five sessions on dry hair.
- Grip and handling
- weight 3 of 13 Whether it stays put with wet, soapy hands, and whether the shape lets you reach the back of the head without twisting your wrist.
- Coverage
- weight 2 of 13 How much scalp one pass covers, and whether the tips reach the scalp through thick hair instead of skating over the top.
- Wet and dry use
- weight 2 of 13 Tested in the shower with shampoo and dry on unwashed hair. Some tools only work in one of those.
- Build quality
- weight 2 of 13 Tip retention, seam quality and whether anything loosened, discoloured or snagged hair over the test period.
- Cleaning
- weight 1 of 13 How easily hair, oil and product residue come out, and whether it dries without trapping water.
Electric scalp massager (Scalp tools)
7 criteria, weights total 14
- Massage strength
- weight 3 of 14 Whether the motor keeps working against the resistance of a real head of hair rather than stalling, across every speed setting.
- Grip and handling
- weight 2 of 14 One-handed use with wet, soapy hands, and whether you can reach the crown and nape without awkward angles.
- Coverage
- weight 2 of 14 How much scalp the head covers per pass, and whether the nodes reach the scalp through thick hair.
- Battery and charging
- weight 2 of 14 Measured runtime from full charge at the highest setting, recharge time, and whether the charging port survives shower use.
- Water resistance
- weight 2 of 14 The stated IP rating, checked against what actually happens over repeated shower sessions.
- Noise
- weight 1 of 14 How loud it is against the skull, where bone conduction makes a quiet motor sound much louder than it measures.
- Build quality
- weight 2 of 14 Seals, button feel, node retention and whether anything degraded over the test period.
Scalp brush (Scalp tools)
6 criteria, weights total 13
- Bristle feel
- weight 3 of 13 Stiffness and tip finish on the scalp, judged on both a sensitive and a non-sensitive tester where possible.
- Grip and handling
- weight 2 of 13 Whether the handle or strap holds with wet hands and lets you work the whole scalp.
- Detangling and snagging
- weight 3 of 13 Whether it pulls hair out or catches on knots, counted over repeated use on fine and thick hair.
- Wet and dry use
- weight 2 of 13 Tested with shampoo in the shower and dry on unwashed hair.
- Build quality
- weight 2 of 13 Bristle retention, pad adhesion and condition after the test period.
- Cleaning
- weight 1 of 13 How much hair and residue the pad traps, and how easily it comes out.
Scalp scrubber (Scalp tools)
5 criteria, weights total 12
- Bristle feel
- weight 3 of 12 Silicone tip softness and flex on the scalp over at least five washes.
- Grip and handling
- weight 3 of 12 Whether it stays in your hand when covered in shampoo, and whether the shape reaches the nape.
- Lather and distribution
- weight 2 of 12 How well it spreads shampoo to the scalp instead of only through the hair.
- Build quality
- weight 2 of 12 Whether the silicone tears, stains or holds smell over the test period.
- Cleaning and drying
- weight 2 of 12 Whether water drains or pools, and whether anything grows in it between uses.
Scalp scrub (Scalp care)
5 criteria, weights total 11
- Exfoliation
- weight 3 of 11 How much visible flaking and buildup it removes in one wash, judged against the tester's usual shampoo.
- Rinse-out
- weight 3 of 11 Whether grit, oil or film is left behind after a normal rinse, and how much water it takes.
- Hair feel afterwards
- weight 2 of 11 Whether hair is left coated, squeaky or weighed down once dry, with and without conditioner.
- Tolerance
- weight 2 of 11 Any stinging, tightness or redness reported during the test period. Not a safety test: a tolerable product can still irritate you.
- Scent
- weight 1 of 11 Strength and how long it lingers. Subjective, and weighted accordingly.
Scalp oil (Scalp care)
5 criteria, weights total 11
- Spreadability
- weight 3 of 11 Whether the applicator or dropper puts oil on the scalp rather than the hair, and how far a single dose goes.
- Greasiness
- weight 3 of 11 How the scalp and roots look and feel a few hours after application, and whether it is wearable overnight only or also during the day.
- Wash-out
- weight 2 of 11 How many shampoos it takes to remove, which is where heavy oils cost you more than they give.
- Tolerance
- weight 2 of 11 Any stinging, itch or congestion reported over the test period. Not a safety test.
- Scent
- weight 1 of 11 Strength and persistence, including essential-oil loads strong enough to be a problem on a pillow.
Scalp serum (Scalp care)
5 criteria, weights total 11
- Applicator
- weight 3 of 11 Whether the nozzle, dropper or comb tip delivers product to the scalp in a controlled way, and whether it drips.
- Absorption
- weight 3 of 11 How long it takes to stop feeling wet, and whether you can style or sleep on it afterwards.
- Residue
- weight 2 of 11 Flaking, stickiness or crust at the roots after drying, and after a second application on day two.
- Tolerance
- weight 2 of 11 Any stinging, itch or redness reported over the test period. Not a safety test.
- Scent
- weight 1 of 11 Strength and persistence on the scalp through the day.
LED / red-light device (Hair-growth devices)
6 criteria, weights total 14
- Fit and comfort
- weight 3 of 14 Whether it stays in position hands-free for a full session, and how it sits on different head sizes.
- Scalp coverage
- weight 3 of 14 Which areas the emitters actually reach, mapped against where thinning usually starts. Coverage, not dose.
- Session practicality
- weight 2 of 14 Stated session length and frequency, and whether that fits into a real week without rearranging your evenings.
- Heat
- weight 2 of 14 Scalp surface temperature by the end of a full session, and whether it ever became uncomfortable.
- Controls and usability
- weight 2 of 14 Timers, cable management, charging and how obvious it is that a session finished properly.
- Build quality
- weight 2 of 14 Hinges, emitter housings, cable strain relief and condition after the test period.
Laser cap or helmet (Hair-growth devices)
6 criteria, weights total 14
- Fit and comfort
- weight 3 of 14 Whether the shell sits level and stays put for a full hands-free session, across head sizes.
- Scalp coverage
- weight 3 of 14 Where the diodes actually sit against the scalp, mapped against the areas people most want treated. Coverage, not dose.
- Weight and balance
- weight 2 of 14 Measured weight, and whether it stays comfortable or starts pressing by the end of a session.
- Battery and sessions
- weight 2 of 14 Measured sessions per charge against the claim, and how the battery pack is carried.
- Heat
- weight 2 of 14 Scalp temperature by the end of a full session, and whether airflow or padding manages it.
- Build quality
- weight 2 of 14 Shell rigidity, diode housings, connector quality and condition after the test period.
Laser comb (Hair-growth devices)
6 criteria, weights total 13
- Ease of use
- weight 3 of 13 Whether the stop-and-move routine is realistic to follow correctly for a whole session, every session.
- Scalp coverage
- weight 3 of 13 How much scalp a full prescribed session actually covers, and how long that takes. Coverage, not dose.
- Grip and handling
- weight 2 of 13 Whether the handle stays comfortable for the whole session, including reaching the crown.
- Hair parting
- weight 2 of 13 Whether the teeth part hair down to the scalp, which is the difference between treating skin and treating hair.
- Heat
- weight 1 of 13 Scalp and handle temperature by the end of a session.
- Build quality
- weight 2 of 13 Teeth, hinge, battery door and condition after the test period.
What this methodology does not tell you
We test usability, build and experience. We do not run clinical trials, and nothing here measures whether a product grows hair. For that, read the research summaries, which grade the published evidence and are checked by a medical reviewer.
Found a problem with how we scored something? Tell us.