Wahl Blade Size Chart

Detachable blades follow a numbering convention shared across several manufacturers, where a higher number means a shorter cut:

Because the shortest blades cut close enough to catch skin, they are normally used with a guard on top rather than bare - the blade sets the base length and the guard sets what you actually leave.

Guards run the opposite way and in eighths of an inch: #1 leaves about 3 mm, #2 about 6 mm, #4 about 13 mm, #8 about 25 mm. Full mapping is on the clipper guards page.

The practical consequence: "a number two" means completely different things depending on whether the person is talking about a guard or a detachable blade. In a barber's chair it is nearly always a guard. In a grooming context it is often a blade.

On adjustable-taper clippers the side lever changes cut length continuously between the blade's closed and open positions - typically somewhere around 1 mm to 3 mm depending on the machine.

This matters when reproducing a cut. Guard number plus blade type is not the full description if the lever moved; the same guard over an open lever leaves visibly more hair than over a closed one. If a haircut came out right, note the lever position too.

Listings are inconsistent about which system they are quoting, so check for a length in millimetres or inches rather than trusting the number alone. A blade listed as "#10 - 1.5 mm" is unambiguous; one listed as "size 10" with no length could be either system.

If the listing gives no length at all and no compatible-model list, treat that as a reason to look elsewhere. The information is standard, and its absence usually means a generic import with no particular fit in mind.