You’ve clipped dogs for a while. You know the feel of a #10 under a Poodle’s foot, and you know a #7F reads plush on a short double coat. But then a customer hands you a used Wahl clipper, says “just use a #30,” and walks away — and you’re staring at a blade label wondering if Wahl’s numbers mean the same thing as Andis’s.
They usually do. But not always. Here’s the answer-first breakdown.
The Core Rule: Higher = Shorter
Numbers go up, hair left behind goes down. Roughly:
- #3F / #3¾ = 1/2” (13 mm) — long, plush body
- #5F = 1/4” (6.3 mm) — short and even
- #7F = 1/8” (3.2 mm) — summer clip
- #10 = 1/16” (1.5 mm) — close work (face, feet, sanitary)
- #15 = 3/64” (1.2 mm) — foot pads and close face work
- #30 = 1/50” (0.5 mm) — comb base, vet-adjacent
- #40 = 1/100” (0.25 mm) — surgical
- #50 = 0.4 mm — surgical (Wahl’s closest)
But the chart above is a lie. Or at least a half-truth. The numbers are usually consistent across brands — Andis and Oster agree on most of them. Wahl breaks the rule in three places, and one of those breaks matters to pet groomers daily.
Where the Names Stop Matching Reality
The #3F Trap
Oster calls it a #3F. Andis calls it a #3¾FC. They’re the same blade: 1/2” (13 mm).
Wahl also calls theirs a #3F. But Wahl’s #3F cuts 10 mm — nearly 3 mm shorter. Same label on the box. Different cut on the dog.
If you’re grabbing a #3F blind for a Shih Tzu plush cut, and you don’t notice which brand is in your hand, you’ve just trimmed an Oster or Andis #3F to length, then grabbed a Wahl #3F thinking it’s the same — and the dog now looks shorn instead of plush. This is the trap that costs calls to upset customers.
The rule: Any time you’re shopping a #3-family blade (especially #3F), check the brand’s stated cut length, not just the number.
The Finish (F) vs Skip-Tooth Split
Look at a blade label and you might see:
- #7F — finish-tooth
- #7 (or #7 skip) — skip-tooth
The cut length is the same: both leave 1/8”. The difference is tooth spacing.
Finish-tooth (F) has teeth close together, like a regular saw blade. It cuts smooth and even — the look you want on a final coat.
Skip-tooth has gaps between the teeth. It cuts more aggressively and doesn’t jam on tangled, dirty, or matted hair. Andis’s official guidance is blunt: use skip-tooth before the bath (on coat that might be matted or muddy), then finish-tooth after bathing for the smooth final cut.
Never use skip-tooth on a cat — Andis prints that warning right on the chart.
The Surgical Blade Surprise: #50 > #40
At the short end, the “higher number = shorter” rule collapses.
- Andis #40 = 0.25 mm (1/100”)
- Wahl #50 = 0.4 mm — which is longer than the #40
This matters only if you’re in vet territory, which pet groomers mostly aren’t. But it breaks the rule, so it’s worth knowing.
Snap-On Combs: The Blade Underneath Matters More Than the Number
You own a Wahl #30 blade and a set of snap-on metal combs in sizes 1/8” through 1”. You snap the 1/2” comb onto the #30 and start clipping.
The 1/2” comb label tells you the final hair length — 13 mm left on the dog.
The #30 blade underneath is there to keep the comb’s teeth sharp at the root. It’s not the cut length; it’s a base. Every manufacturer says so: Wahl’s guidance is “put a #30 underneath”; Andis’s guide says the same; Oster writes breed recipes as “30 & 1” UC” (Universal Comb).
For snap-on work, the blade number is almost invisible. The comb’s label is what matters. The blade just has to be short enough (a #30, or #10, or #15) to let the comb do the cutting.
This is covered in depth on the full blade chart, which walks through every blade size and comb pairing.
The 5-in-1 Switcheroo
If your clipper is a Wahl Bravura or Arco (or Andis Pulse Li 5), it doesn’t take detachable A5 blades. It takes an adjustable blade that slides between five settings: #9, #10, #15, #30, #40.
Here’s the trap: those settings look like A5 blade numbers. They aren’t. A Wahl 5-in-1 #30 setting cuts roughly 0.8–1.3 mm — nearly double an A5 #30, which cuts 0.5 mm.
If you learned grooming on an A5 clipper and grab a 5-in-1 thinking the numbers transfer, you’ll cut way longer than you expect. The numbers are identical, the lengths aren’t.
Check your clipper first — does the blade snap on flat with a lever, or does it slide and lock with a tiny screw? Snap-on = A5. Sliding with a screw = 5-in-1. The two systems don’t share blade numbers. Our blade & comb finder tool identifies your system in one click.
What Each Number Actually Gets Used For
Body work (everyday pet cuts):
- #3F–#5F: full-coat body lengths, plush to short-but-fluffy
- #7F: summer/kennel clip standard
- Snap-on combs over #30: teddy trims, puppy looks, any longer length without a full-length blade
Sanitary and detail work (per both Andis and Oster official charts):
- Sanitary prep (rear/underbelly): #10
- Paw pads: #15
- Face on Poodles/Schnauzers: #10 or #15
- Matted coat that won’t yield to a finish blade: #7F, or #10 if it’s bad enough
Surgical/vet (not grooming):
- #30, #40, #50: pre-surgical preps, vet clinic contexts
The blade & comb finder also checks your dog’s breed and coat type, then suggests which blade is standard for that breed across the Andis and Oster official charts.
The Bottom Line
Blade numbers are mostly consistent across brands. But watch three things:
- The #3F trap: Wahl’s is shorter than Andis’s and Oster’s by 3 mm. Check the brand’s stated length, not just the number.
- Skip-tooth vs finish (F): Same cut, different tooth spacing. Skip before the bath, finish after — especially on tangled coat.
- 5-in-1 vs A5: Different systems, same-looking numbers, wildly different lengths. Identify your clipper system first.
For the complete blade chart with every size, all breed recommendations from the official Andis and Oster guides, and comb pairings, see the full grooming blade reference. For everything about snap-on combs, guide comb compatibility across brands, and the anatomy of finish vs skip blades, read our detailed blade type and technique guide.
This guide is based on official manufacturer blade charts (Andis Form #12666, Oster Canine Blade Chart, and Wahl support pages), verified 2026-07-04. For individual dog skin concerns or clipper irritation, consult your veterinarian.