How to Choose Clipper Blade Sizes: #4FW, #15W and #40
By Groomer's Warehouse | Published: 2026-10-31
Category: How-to Guides
Learn how to pick clipper blade sizes by coat, task and clipper system, with practical rules for #4FW, #15W and #40 blades and a step-by-step selection process.
Quick answer
Match the blade to the task, not just the breed: use a #4FW for wider passes on thicker coats, a #15W for larger trimming areas on horses, cattle and large dogs, and a #40 for close work such as pet paws. Then confirm the blade fits your clipper's snap-on system before you buy.
Why blade width and cut length matter more than the number alone
Blade numbers are not a universal ranking from short to long across every brand or clipper system. The cut length and blade width printed for your specific blade are the reliable guide. For example, the #15W is listed as cutting 3/16 inch (1.0 mm), while the #40 is listed as cutting 1/100 inch (0.25 mm). Those are very different jobs, and choosing by number alone can lead to the wrong finish or an uncomfortable clip.
Width changes the workflow. A wide blade covers more surface per pass, which is useful on larger areas or thicker coats, but it can be harder to control around ears, paws and other tight spots. Narrower or finer blades give more control but take longer on big body areas.
Where each blade earns its place
The #4FW is a wide blade intended for efficient cutting through thicker coats. Reach for it when you need to move quickly over a broad area and the coat is heavy enough that a standard blade feels slow.
The #15W is designed for larger trimming areas and is specifically suited to horses, cattle and large dog breeds. Its 3/16-inch cut makes it a practical choice for body work on larger animals rather than fine detail.
The #40 is a close-cutting blade at 1/100 inch, which makes it a sensible option for pet paws and other tight, precise areas where you want very short hair. It fits snap-on A Series clippers and is listed as compatible with Heiniger, Oster, Andis, Conair, Wahl, Laube, Thrive and other clippers using a snap-on/off blade system.
The compatibility check that prevents returns
Blade fit is the most common source of frustration. The #40 is explicitly listed for A Series snap-on clippers and compatible brands, but the #4FW and #15W records do not list a clipper system. Before ordering those, check your clipper model and its blade attachment style against the product listing. If the listing does not state compatibility, treat that as a decision limitation and confirm with the seller rather than assuming it will fit.
Also check the animal. The #15W is described for horses, cattle and large dog breeds, so it is not the first choice for a small dog's face or a cat. The #40's close cut is useful on paws but should be used with care on thin or sensitive skin.
How to choose your clipper blade in five steps
- Identify the task and the animal: Decide whether you are doing broad body work, trimming a large animal, or close detail such as paws. Write down the species and the area before looking at blade numbers. Common mistake: choosing a blade by breed reputation instead of the actual coat and area in front of you.
- Check your clipper's blade system: Look at your clipper manual or the old blade and confirm whether it uses a snap-on A Series system or another attachment. Compare that to the product listing, and if compatibility is not stated, ask before buying. Checkpoint: a blade that does not snap on securely should not be used, even if the cut length is right.
- Match cut length to the finish you want: Use the stated cut length, not the number alone. A 1/100-inch blade like the #40 is for very close work, while a 3/16-inch blade like the #15W leaves noticeably more hair. Common mistake: assuming a higher number always means a longer cut across every brand.
- Choose width for the area and coat: Pick a wide blade such as the #4FW for broad passes on thicker coats, and a standard or finer blade for controlled work around tight areas. Wide blades save time on large surfaces but are less precise in corners. Checkpoint: if the coat is matted or very thick, the blade still needs to move freely; do not force a wide blade through a knot.
- Test on a small area first: Run the blade briefly on a small, safe area and check the finish and the animal's comfort before committing to the full clip. Stop if the blade pulls or heats up. Common mistake: clipping the whole animal before noticing that the blade length or width is wrong for the job.
Product facts at a glance
- Groomer's Warehouse #4FW Clipper Blade: Wide #4FW blade designed to cut efficiently through thicker coats. Choose it when you need faster coverage on a heavy coat rather than fine detail.
Groomer's Warehouse #4FW Clipper Blade - Groomer's Warehouse #15W Clipper Blade: #15W blade cuts 3/16 inch (1.0 mm) and is intended for larger trimming areas on horses, cattle and large dog breeds. It suits body work on larger animals, not close work on small or sensitive areas.
Groomer's Warehouse #15W Clipper Blade - Groomer's Warehouse #40 Clipper Blade: #40 blade cuts 1/100 inch (0.25 mm) and fits snap-on A Series clippers, including several listed brands. Its close cut and broad clipper compatibility make it a practical choice for pet paws when your clipper uses that system.
