Comb numbers
Guard numbers
A comb number is not a length. It is a position in a series, and the series is usually eighths of an inch counted upward from the skin. The converter below prints that series and the arithmetic behind it, and it is deliberately tied to no appliance on this site.
Numbers and fractions
The widely used series counts in eighths of an inch: the first position leaves an eighth standing, the fourth leaves half an inch, the eighth leaves a whole one. Converted into millimeters the steps are a little over three at a time, which is why the metric figures are rarely round.
That is the whole of the arithmetic. Everything else people believe about comb numbers is either a property of a particular appliance or a property of the hair the comb is sitting on.
Whose numbers these are
Makers do not agree. One brand’s number three may leave a different length standing from another’s, and some appliances abandon numbers altogether in favor of a dial marked in millimeters.
So the series below is the common one and nothing more. The numbers stamped on the combs in your own box come from the documentation in that box, and no appliance quoted anywhere on this site has been tied to the table below.
Density and angle
A comb does not ride on skin. It rides on the hair beneath it as much as on the face, so a dense beard holds the comb slightly further out than a sparse one and finishes marginally longer at the same setting.
The angle matters as much. A comb held flat leaves the stated length; the same comb tilted leaves more, because only its leading edge is touching. This is the usual explanation for a beard that comes out longer than the number promised.
Where numbers stop
Past the far end of the usual range, combs become impractical: they are long, they flex, and they no longer hold hair reliably against the blade. That is the point where scissors and a comb do more than any attachment.
It is also the point where cutting to a number stops being useful, because a beard long enough to lie over itself is being shaped rather than set to a length.
Comb number to length
Comb number
Read it in
- Length left standing
- 9.52 mm left standing
- Comb number
- 3
the length where a beard starts holding a shape on its own
This is the series most kits are numbered on. The numbers stamped on your own combs come from the documentation that arrived with your own appliance, and no product on this site is tied to the table above.
The arithmetic
- inches left standing = guard number ÷ 8
- millimeters left standing = guard number × 25.4 ÷ 8
What it does not account for
- The angle the appliance is held at, which changes the result more than a single comb number does.
- The direction of the pass, since hair cut against the way it lies sits shorter than the same number cut with it.
- How dense the beard is, because the comb rides on the hair under it.
- A worn cutting edge, which leaves hair longer than the number suggests.
Where this goes wrong
Trusting a number across brands
A setting that worked on a previous appliance is used on a new one, and the beard comes out at a length nobody chose.
Cut one small patch at the new appliance’s setting and look before committing the whole face to it.
Tilting the comb
Only the leading edge of the guard touches, the blade sits further from the skin than the number implies, and the result is uneven rather than long.
Keep the flat of the comb against the face and move slowly enough to feel when it lifts.
Cutting wet to a number
Wet hair lies longer than dry hair, so a length judged wet turns out shorter once it dries and lifts.
Set length on a dry beard, and leave water for the shaving rather than the trimming.
Cautions
- StopTwo things mean stopping rather than taking one more pass. Skin that is broken, raised, sore or already inflamed, which is a doctor’s call and not something to draw a blade across. And a line so far out of true that a shorter setting only chases it, which is a barber’s. Neither of them improves by carrying on.
- NoteReplacement foils, cutters and heads come from the list printed in the appliance’s own documentation. A part that seats is not the same as a part the maker names.
Where to look next
- Stepping down safely
What to do when the number you want is several settings below the one you are at.
- Beard Trimmers
The appliances these numbers belong to, including the ones that count settings rather than combs.
- Cheeks and jawline
The area where one length across the whole panel answers most of what looks like patchiness.