Dog Grooming Blade Length Chart: Blades and Guards in mm and Inches

A dog grooming blade length chart maps each blade number to the coat it leaves. The #3 blade leaves 13 mm (1/2 inch); #5 leaves 6.3 mm; #7 leaves 3.2 mm; #10 leaves 1.6 mm; #30 leaves 0.5 mm; and #40 leaves 0.25 mm. Higher blade numbers cut shorter, and guard combs extend any blade to leave 3 to 25 mm of coat.

The dog grooming blade length chart answers one of the most persistent points of confusion in clipping: why higher blade numbers leave less hair, not more. This reference covers every standard blade from #3 to #40 with exact mm and inch measurements, maps guard comb sizes to the lengths they produce, and includes a reverse lookup so you can identify the right blade or comb starting from the coat length you want to leave, rather than from the blade number itself.

The Main Dog Grooming Blade Length Chart: Blades #3 to #40

The core of any dog grooming blade length chart is the mapping from blade number to the exact length of coat it leaves when clipping with the grain on a clean, dry and fully de-matted coat. The counter-intuitive logic is worth stating once clearly: a lower blade number leaves more hair, and a higher blade number cuts closer to the skin, because the numbering reflects the density of teeth per inch on the blade rather than the length of the resulting cut.

The against-grain figures in this dog grooming blade length chart reflect a 20 to 40 percent shorter result than the with-grain measurement, because clipping against the direction of coat growth lifts the hair shaft before the blade passes, producing a noticeably closer finish than the standard figure suggests. The "F" designation after a blade number stands for Finishing: these blades have more closely spaced teeth and produce a fractionally smoother, slightly shorter result of approximately 0.2 to 0.5 mm. For a full guide to blade applications and coat-type recommendations organised by blade number and use case rather than by hair length, see the Dog Clipper Blade Chart: Size, Use, and Which Blade for Every Coat Type on the EliteTrim blog.

Understanding F Blades vs Regular Blades

Beyond the mm measurements, the distinction between F (Finishing) and standard blades affects texture and surface quality as much as it affects coat length.

When to choose F blades

F blades are the better choice for body clips on smooth-coated breeds and for any area where an even, track-free finish matters, because their closely set teeth move through the coat with greater uniformity. On thick, double-coated or heavily textured coats, a standard non-F blade is often the more practical option: the wider-spaced teeth move through volume more efficiently without the blade bogging down or heating as quickly during extended work. The blade length chart numbers remain consistent between F and non-F versions of the same blade; the F designation affects surface quality and finish, not the mm measurement shown in the table above.

Skip-tooth blades and why they are not in this chart

Skip-tooth blades, which feature alternating long and short teeth, are not included in the standard dog grooming blade length chart because they do not produce a consistent, measurable coat length. Their purpose is to move through mats and dense, knotted coats by parting the hair rather than cutting it to a set depth, which makes them a preparation tool rather than a finishing one. After skip-tooth work has opened the coat sufficiently, a finishing blade produces the measured result shown in the chart above. Including skip-tooth blades in a length reference would be misleading, since their output depends entirely on coat condition rather than on a fixed mm figure.

Guard Comb Length Chart: Attachment Combs #1 to #8

Guard combs, also called attachment combs or snap-on combs, are the most practical option for home groomers who need a longer, fluffier coat finish without purchasing individual blades for every length increment. All measurements in this section of the dog grooming blade length chart assume the guard is used over a #10 blade as the base, which is the recognised industry standard for guard comb use.

Guard #4 over a #10 blade produces 13 mm, equivalent to a bare #3 blade, but with the added safety margin of the comb preventing the blade from making direct contact with the skin. This makes Guard #4 the recommended starting point for home groomers new to using this dog grooming blade length chart, because the comb tolerates minor angle variations better than a bare blade does on uneven topography. One condition applies consistently to all guard comb use: combs perform as this chart predicts only on coats that are completely dry, fully de-matted and brushed through to the skin level. For guidance on the coat preparation routine that ensures blades and guard combs produce the results this chart promises, see Do You Bathe a Dog Before Grooming? The Correct Order Explained on the EliteTrim blog.

Reverse Lookup: Find the Right Blade from the Hair Length You Want

The conventional dog grooming blade length chart runs from blade number to mm. This reverse lookup inverts that reference: if you already know how long you want the coat, find the right blade or guard here without needing to hold the full number-to-length mapping in memory.

Hair lengths above 13 mm have no direct bare-blade equivalent in the standard dog grooming blade length chart, which means guard combs are the only safe option for leaving 16 mm or more. There is no bare clipper blade designed to safely produce 19 to 25 mm of remaining coat, because the blade has no mechanism for maintaining a consistent distance from the skin at that depth, and any attempt without a guard results in an uneven finish with a high risk of skin contact. Groomers and home owners targeting the longest lengths in the reverse lookup should also note that coats of 19 to 25 mm require the greatest brushing commitment to prevent matting from establishing between grooming sessions.

How Coat Type Changes What the Chart Predicts

The mm measurements in this dog grooming blade length chart represent performance on a clean, fully dry and completely de-matted coat. Both coat type and coat condition shift these figures in predictable ways that are worth accounting for before selecting a blade.

Dense and double coats

A #5F blade on a Labrador's double coat produces approximately 6.3 mm as the chart shows, but the same blade on a dense, tightly curled Poodle coat produces a slightly shorter result, because the fine, closely packed fibres compress more under the blade teeth and reduce the effective cutting depth. Dense coats also accelerate blade wear during a session, causing a progressive drift toward shorter results as the blade dulls over time. Thorough pre-clip preparation, including complete blow-drying and full brushing to lift the coat away from the skin before any clipping begins, is the most effective way to keep blade chart results consistent across the full dog. For a complete pre-clip routine that supports accurate blade chart results, see Dog Grooming Steps on the EliteTrim blog.

Damp coats and the most common chart discrepancy

Wet or damp coats consistently produce a shorter result than the dog grooming blade length chart indicates, because damp hair lies flat and compresses under the blade rather than standing away from the skin as a fully dry, fluffed coat does. A #7F used on a damp Cockapoo coat may produce 2 mm rather than the 3.2 mm shown in the chart: a difference significant enough to change the visual outcome of the groom entirely. The chart is calibrated to 100 percent dry coat at skin level, not just at the surface, and finishing a clip on a coat that feels dry to the touch but retains moisture at the base is one of the most common reasons chart predictions fail in practice.

Using This Dog Grooming Blade Length Chart Safely

The measurements in this chart are reference figures that assume correct technique and well-maintained equipment. Three practical rules cover the most common clipper errors and injuries that occur when applying the chart in real grooming conditions.

First, monitor blade temperature throughout the session: clipper blades heat to uncomfortable levels within minutes of continuous use, and clipper burn can occur without leaving visible marks on the coat surface. Testing the blade against the back of the hand every four to five minutes and switching to a cool replacement or applying blade coolant spray keeps skin-contact temperature within a safe range. 

Second, respect the matting exception without compromise: guard combs should never be forced through a mat, because the comb compresses the matted hair against the skin and places the blade in contact with the skin beneath it rather than with the hair above it. 

Third, always start at a longer setting than the chart indicates you need, because no blade can restore removed coat during a session. For a broader guide to clipper safety across equipment types, see Can You Use Human Clippers on Dogs? Safety Guide and Tips. 

For professional-grade dog clippers and compatible guard combs matched to the blade sizes in this dog grooming blade length chart, see the EliteTrim dog clippers and trimmers collection.

Frequently Asked Questions

Why do higher blade numbers cut shorter in the dog grooming blade length chart?

The numbering system dates from when clipper blades were specified by teeth per inch rather than by the length of coat they leave. More teeth per inch produces a finer, closer cut. The convention has been standardised across all major professional blade manufacturers, including Andis, Oster and Wahl, but it remains counter-intuitive for anyone encountering the system for the first time.

What does the F mean in a blade number like #7F?

F stands for Finishing. An F blade has more closely spaced teeth than the same blade number without the F, which produces a fractionally smoother surface and a marginally shorter result, typically 0.2 to 0.5 mm. The mm measurements in this dog grooming blade length chart assume the F version where an F variant is available, since F blades are more commonly used for finished work on pet coats.

Can I use guard combs over any blade?

Guard combs are calibrated to work over a #10 blade as the standard base. Using a guard over a shorter blade such as a #30 or #40 produces a shorter-than-expected result, because the base blade has already cut closer before the guard's comb depth is added. For the guard comb section of this dog grooming blade length chart to predict accurately, always use a #10 blade as the base.

Why is the against-grain result so much shorter?

Clipping against the direction of coat growth lifts the hair shaft before the blade passes, causing it to cut closer to the root than it would when following the coat's natural direction. This typically produces a result 20 to 40 percent shorter than the with-grain figure shown in the chart. A #7F used against the grain produces approximately 2 mm rather than the 3.2 mm shown in the standard dog grooming blade length chart.

Does this blade length chart apply to all clipper brands?

The blade number system is standardised across all major professional clipper brands, so the mm figures in this dog grooming blade length chart apply consistently across Andis, Oster, Wahl and most professional-grade alternatives. Minor variations of 0.1 to 0.3 mm can occur between manufacturers depending on production tolerances. Guard comb sizes follow the same numbering convention but can vary slightly in actual comb depth between brands; always verify with the specific brand's published specifications when precision is critical.

This dog grooming blade length chart covers every standard blade from #3 to #40, the full guard comb range from #1 to #8, and a reverse lookup to identify the right blade or comb from the coat length you want rather than from the blade number. Every measurement assumes a completely dry, fully de-matted coat: coat condition is the primary variable that determines whether the chart's predictions hold accurately in practice.