A5 Blade Codes Decoded: What 3F, 4FW, 7FW and 10W Actually Mean

A5 blade codes look like a system until you try to read one. 3F, 4FW, 7FW, 10W, 40# — the numbers run in both directions and the letters appear to mean nothing in particular. They are actually two independent pieces of information stacked into one label: a cutting height and a blade format. Once you separate the two, every code in the range decodes in seconds. This article sets out the rules, the full length chart, and the things a code deliberately does not tell you — which is where most buying mistakes happen.

The three rules, in full

1. The number is the cutting height — how much coat is left on the horse. It is not millimetres on the label and it is not a model sequence.
2. Lower number, longer cut. A #40 leaves 0.25 mm, a #3F leaves 13 mm. The scale runs the opposite way to what most people assume, and it is easy to remember backwards.
3. The letter is the format — F for the finish comb, W for the wide body. Letters never change the cutting height of the number they sit next to.

Part 1 — the number: cutting height

The A5 numbering is a legacy imperial scale, not a metric one. Each number corresponds to a fraction of an inch of coat left on the animal, and the fractions were inherited from the original detachable blade ranges rather than calculated. That is why the numbers are neither evenly spaced nor complete: the range goes 3, 4, 5, 7, 8.5, 9, 10, 15, 30, 40, with nothing in between, because sizes were added over decades as demand appeared.

Two practical consequences follow from this table. First, adjacent numbers are not evenly spaced: #9 to #8.5 is 0.4 mm, while #5F to #4F is 3.2 mm. Second, the high numbers do not mean "big blade" — a #40 is the smallest cut in the range, not the largest.

Part 2 — the letters: format, not length

F = finish (full-tooth) comb

An F blade has teeth along the full length of the comb, which is what produces a smooth, even finish. The alternative in most A5 ranges is a skip-tooth comb of the same number: same cutting height, fewer teeth, wider gaps. Skip-tooth blades feed faster through thick or dirty coat and leave a more visible pattern, which is why they are used for blending and for taking down bulk rather than for a finish. So 7F and a skip-tooth 7 both leave 3.2 mm — the difference is the tooth pattern, not the length.

W = wide body

W marks the wide version of the same number: identical cutting height, wider cutting surface. Our own wide blades are specified at roughly 36% more cutting surface than the standard body of the same number, and that figure is broadly representative of wide blades across the trade rather than an industry standard — other manufacturers do not always publish a percentage.

Not every brand writes the letters the same way

The number is widely shared across A5 manufacturers; the letter conventions are less consistent. Wide blades may be labelled 10W, 10 Wide or Wide 10 depending on the brand and the era of the packaging. Some ranges also add intermediates and suffixes of their own. This is why the only reliable comparison between brands is the cutting height in millimetres or inches — not the code alone.

Part 3 — decoding real codes

Notice what the codes in that table do not contain: no millimetre value, no comb width, no cutter material, no clipper brand. The code identifies a length and a tooth format, and nothing else.

Part 4 — five things a code cannot tell you

1. The cutter material. Ceramic and stainless steel cutters sit on the same blade. A 10W can be bought with either; the code does not change. If heat and longevity matter, ask for the cutter separately — see ceramic vs stainless steel clipper blades.
2. The actual width. "Wide" is a comparison within a brand, not a dimension. Two manufacturers' wide blades are not necessarily the same width, and only some publish the percentage.
3. Brand fit. A5 is a standardised physical system, not a brand, so an A5 blade generally seats on any A5-compatible clipper — but blades for the Oster 76 series or for livestock shears are a different system entirely and will not fit. Check the clipper model, not the name on the blade.
4. Cutter tooth count. Our ceramic cutters are 18 or 25 teeth and our stainless cutters 22 teeth, but tooth counts are manufacturer-specific. Two cutters that both fit will not necessarily have the same count.
5. Whether you already own it. Because most A5 clippers ship with a 10# fitted, the first blade buyers add is usually a 10W (for body speed) or a 9# (for sensitive horses) — not another 10#.

Part 5 — why the numbers behave so oddly

Three quirks explain almost every "this chart makes no sense" question:

• It is imperial, not metric. The numbers are tied to fractions of an inch — 1/16″, 5/64″, 1/8″, 1/4″. Converting to millimetres produces the familiar 1.5, 2, 3.2 and 6.3 figures, which look arbitrary because they are conversions, not design values.
• The gaps are historical. Sizes were added when a job needed a length between two existing blades. That is how 8.5 and 9 came to sit so close to each other while 10 and 15 sit 0.3 mm apart.
• Some sizes are not universal. 8.5 is common but not carried by every brand; some ranges also add their own intermediates. If a particular length matters to you, buy on the millimetre figure and confirm the model is in the supplier's range.

Part 6 — how to check any chart you are given

Blade charts are copied from one another across the trade, mistakes included, so it is worth being able to test a chart in a few seconds before you order against it:

1. Compare in one unit only. Do not read millimetres from one row and inches from another. Convert both or neither.
2. Spot-check three anchors. Whatever the chart says, #10 must be 1.5 mm (1/16″), #7F must be 3.2 mm (1/8″) and #4F must be 9.5 mm (3/8″). If those three are right, the rest of the table is usually sound.
3. Check the direction. If a chart tells you that a higher number leaves more coat, it has the scale inverted — use another chart.
4. Check the W rows. Every wide version must repeat the same cutting height as its standard counterpart. A table where 10W shows a different length from 10# has mixed up the format and the length.
5. Check the system, not the brand. If the chart mixes A5 blades with Oster 76 or livestock blades, the numbers are no longer comparable.

Where the whole range sits, at a glance

The W versions sit alongside the same lengths rather than in a separate zone: 3FW, 4F and 4FW, 5F and 5FW, 7F and 7FW, plus the 9#, 10# and the 10W wide version of the 10# at the same 1.5 mm.

Frequently asked questions