Will a #40 blade fit my clipper?

#40 detachable blades follow the A5 standard, so they interchange across A5-style clippers from Andis, Oster, Wahl (KM series), and Heiniger. They do not fit 5-in-1 adjustable-blade clippers (like the Wahl Bravura) or screw-on home clippers — those use their own blade systems.

Is a #40 blade safe to use at home?

Close-cutting blades heat up fast and can burn skin. Check blade temperature against your forearm every few minutes, use coolant spray, and keep this length away from thin-skinned areas unless you've been shown how. When in doubt, this is a job for a professional groomer.

Clipper blades Checked against maker charts

The #40 clipper blade

A #40 blade leaves about 1/100" (0.25 mm) of coat.

Cut length

1/100"(0.25 mm)

Length from the Andis chart; Oster sells a #40 but publishes no official length. Andis also makes a dedicated surgical stainless version (#64084).

Type

Close-cutting / surgical length

What the #40 is used for

Surgical/vet prep — this is the blade clinics use before procedures
Andis allows it under a Universal comb; Wahl and Oster don't list #40 as a comb base
Not a grooming body blade — reserve it for vet contexts

Which clippers it fits

#40 detachable blades use the A5 standard — they interchange across Andis, Oster, Wahl KM-series, and Heiniger A5-style clippers regardless of which brand made the blade. They do not fit 5-in-1 adjustable clippers (Wahl Bravura/Arco) or screw-on home clippers, which take their own blade systems.

Leaves more coat

#50

All blade sizes

3/4HT 5/8HT #3F / #3¾ #4F #5F #6FC #7F #7 skip-tooth #8½ #9 #10 #15 #30 #50#40

FAQ

How much hair does a #40 blade leave?: A #40 blade leaves about 1/100" (0.25 mm) of coat. Length from the Andis chart; Oster sells a #40 but publishes no official length. Andis also makes a dedicated surgical stainless version (#64084).
Will a #40 blade fit my clipper?: #40 detachable blades follow the A5 standard, so they interchange across A5-style clippers from Andis, Oster, Wahl (KM series), and Heiniger. They do not fit 5-in-1 adjustable-blade clippers (like the Wahl Bravura) or screw-on home clippers — those use their own blade systems.
Is a #40 blade safe to use at home?: Close-cutting blades heat up fast and can burn skin. Check blade temperature against your forearm every few minutes, use coolant spray, and keep this length away from thin-skinned areas unless you've been shown how. When in doubt, this is a job for a professional groomer.

Sources