How to Cut PEX Tubing

Learning how to cut PEX tubing is the first skill you need for working with the most popular water supply pipe in new American homes. PEX, short for cross-linked polyethylene, is flexible, freeze-resistant, and far easier to install than copper or CPVC. It is also easy to cut, but the cut has to be square and clean, or the crimp or push-fit connection will leak. A good cut takes seconds with the right tool, and a bad cut is the most common reason a PEX fitting fails.

Why a Square Cut Matters for PEX

PEX connections rely on a tight seal between the tubing and the fitting. In a crimp connection, a copper ring is compressed around the tubing and the fitting barb, and the tubing must contact the barb evenly all the way around. In a push-fit connection, an O-ring inside the fitting seals against the outside of the tubing. In both cases, a square cut is what makes the seal work.

When the cut is angled, one side of the tubing is shorter than the other. On a crimp fitting, the short side may not reach far enough onto the barb, leaving a gap where water can leak. On a push-fit fitting, an angled cut can push the O-ring out of position or leave part of the tubing outside the seal. Either way, the joint is unreliable, and a leak inside a wall can cause thousands of dollars in damage before anyone notices it.

A clean cut matters for another reason: PEX fittings are sized to the exact outside diameter of the tubing, and any deformation changes that diameter. A crushed or flattened end will not fit into a fitting properly, and forcing it in can damage the O-ring or the crimp ring. The right cutting tool leaves the tubing round and undamaged, so the fitting slides on smoothly. If you are new to PEX, our guide on PEX pipe types explains the differences between PEX-A, PEX-B, and PEX-C and which fittings each type uses.

Method 1: PEX Cutter (Best Tool)

A dedicated PEX cutter is the best tool for cutting PEX tubing, and it is the tool most plumbers use. It looks like a pair of pliers with a curved, razor-sharp blade, and it cuts by shearing the tubing cleanly rather than sawing or crushing it. A good PEX cutter costs $10 to $20, and it works on all three types of PEX in sizes from 3/8 inch to 1 inch.

To use it, measure and mark the cut point with a permanent marker. Open the jaws, place the tubing in the cradle so the blade lines up with your mark, and squeeze the handles firmly in one smooth motion. The blade should cut through the tubing in a single squeeze. For larger sizes, such as 1-inch PEX, you may need to squeeze, release, and squeeze again as the ratchet advances the blade.

After the cut, inspect the end. It should be perfectly flat and square, with no burr, no deformation, and no ragged edge. Run your finger around the cut edge. It should feel smooth. If you see a slight lip or a bit of unevenness, trim it with a second cut a fraction of an inch further down the tubing. Do not try to fix a bad cut with a knife, because you will make it worse.

Keep the blade sharp. A dull PEX cutter blade crushes the tubing instead of cutting it, which is the most common cause of a bad cut. Most PEX cutters have replaceable blades, and a replacement blade costs $5 to $8. Replace the blade when cuts start looking rough or when you have to squeeze hard to get through the tubing. Some PEX cutters have a built-in deburring feature, but PEX does not need deburring the way copper does, because the cut is already clean and the material is soft.

Method 2: PEX Scissors (Quick and Cheap)

PEX scissors, also called PEX shears, are a simpler and cheaper alternative to a ratchet PEX cutter. They look like heavy-duty scissors with a curved blade, and they work well on smaller sizes of PEX, typically 3/8 inch, 1/2 inch, and 3/4 inch. They cost $8 to $15, and they fit easily in a tool pouch or a pocket.

To use PEX scissors, mark the cut point, place the tubing in the jaws, and squeeze the handles in one firm motion. The blade shears through the tubing cleanly. The cut quality is nearly as good as a ratchet cutter, though the scissors can struggle with 1-inch PEX, where the extra thickness requires more force than most people can apply in one squeeze.

PEX scissors are a good choice for small jobs, such as replacing a single supply line under a sink or adding a short run to a fixture. They are also useful as a backup tool, because they are small and cheap enough to keep in a toolbox alongside a full-size cutter. If you do a lot of PEX work, a ratchet cutter is more comfortable for repeated cuts, because the ratchet mechanism does the work for you. For a handful of cuts, scissors are fine.

One tip: keep the scissors clean. PEX is a plastic, and the blade can pick up small bits of debris that scratch the next cut. Wipe the blade with a rag after each use, and store the scissors with the blade closed so the edge stays sharp.

Method 3: Utility Knife (In a Pinch)

A sharp utility knife can cut PEX tubing when you do not have a dedicated cutter, and it is better than a hacksaw or a saw of any kind. The technique takes a little practice, but it works in a tight spot where a cutter will not fit.

Mark the cut point, then hold the tubing firmly against a solid surface. Place the knife blade on the mark and roll the tubing under the blade, scoring a shallow groove all the way around. Do not try to cut through in one pass. Instead, score the groove, then make a second pass a little deeper, and a third pass to cut through. Three light passes give you a cleaner, squarer cut than one hard push.

Keep your fingers behind the blade at all times, and cut away from your body. A utility knife can slip on the smooth surface of PEX, and the blade is sharp enough to cause a serious cut. Wear work gloves, and if the tubing is in an awkward position where you cannot control the knife safely, stop and use a different tool.

A utility knife is a backup method, not a first choice. The cut is rarely as square as a PEX cutter cut, and it is easy to score the tubing at an angle if you are not careful. Use it for one or two cuts in an emergency, and buy a proper PEX cutter for any job that involves more than a few cuts.

Tools You Should Not Use on PEX

Using the wrong tool on PEX is the fastest way to ruin a fitting. Here are the tools to keep away from PEX tubing.

• Hacksaw. The teeth tear the plastic and leave a rough, jagged edge. The cut is rarely square, and the burr can damage the O-ring in a push-fit fitting or prevent a crimp ring from seating evenly.
• Standard tube cutter. A copper tube cutter works by rolling a wheel around the pipe and squeezing it. On PEX, the wheel crushes and deforms the tubing instead of cutting it. The flattened end will not fit into a fitting properly.
• Reciprocating saw. A reciprocating saw is far too aggressive for PEX. It melts and tears the plastic, leaves a rough edge, and vibrates the tubing enough to loosen nearby connections.
• PVC ratchet cutter. A PVC cutter looks similar to a PEX cutter, but the blade angle is different and the jaws are sized for rigid pipe. It can crush PEX instead of shearing it cleanly. Use a cutter made for PEX.
• Scissors or kitchen shears. Ordinary scissors will crush and deform PEX rather than cutting it. The flattened end will not seal in a fitting.

The rule is simple: use a tool designed for PEX. A dedicated PEX cutter or PEX scissors costs less than $20, and it is the difference between a joint that holds for decades and a joint that leaks the first time the water is turned on. If you are connecting PEX to copper, see our guide on how to connect PEX to copper for the right fittings and technique.

How to Measure and Mark PEX Tubing

Measuring PEX is different from measuring rigid pipe, because PEX is flexible and the length changes as you bend it. Always measure the tubing in place, along the path it will actually take, rather than measuring a straight line between two points. Add a little extra length for the bend, because a tight bend pulls the tubing shorter than a straight run.

When you measure for a crimp fitting, remember that the tubing needs to slide onto the fitting barb far enough to cover the full barb length, usually about 1 inch for a 1/2-inch fitting. Mark the cut point, then measure the insertion depth from the cut point back along the tubing and mark that too. This second mark tells you how far the tubing should slide onto the fitting. If the tubing does not reach the mark, it is not seated fully.

For a push-fit fitting, the insertion depth is deeper, about 1 inch for 1/2-inch PEX and 1-1/8 inches for 3/4-inch PEX. Most push-fit fittings have a depth gauge on the packaging, and some manufacturers sell a small plastic gauge tool. Mark the insertion depth on the tubing with a permanent marker before you push it in, so you can see at a glance whether the fitting is fully seated.

Always leave a little slack in a PEX run. PEX expands and contracts with temperature changes, and a run that is pulled tight will stress the fittings. Leave a gentle curve or a small loop in long runs, and do not pull the tubing taut between supports. A good rule is to leave about 1/8 inch of slack per foot of run, or about 1 inch per 10 feet.

Cutting PEX Mistakes to Avoid

Most PEX cutting mistakes are easy to avoid once you know what to watch for. Here are the ones that cause the most failed connections.

• Using a dull blade. A dull PEX cutter crushes the tubing instead of cutting it. Replace the blade when cuts start looking rough or when you have to squeeze hard to get through.
• Cutting at an angle. An angled cut leaves a gap on one side of the fitting and can push an O-ring out of position. Check that the cut is square by holding the tubing up and looking at the end. If it is angled, cut it again.
• Cutting PEX that is kinked. A kinked section of PEX is damaged and should be cut out, not used. Kinks restrict flow and weaken the tubing. Cut on either side of the kink and use a coupling to join the good sections.
• Not checking the insertion depth. A fitting that is not fully seated will leak. Mark the insertion depth on the tubing and check that the mark lines up with the end of the fitting after installation.
• Cutting in cold weather. PEX becomes stiffer in cold weather, though it does not become brittle the way PVC does. If the tubing is cold, warm it with your hands or bring it indoors before cutting. A cold cut is more likely to be rough.
• Reusing a bad cut. If a cut is angled, crushed, or ragged, do not try to fix it. Cut it off and start again. PEX is cheap, and a fresh cut costs a few cents of tubing. A leaking joint costs far more.

Cutting PEX tubing is one of the easiest plumbing skills to learn, and it is the gateway to a whole range of do-it-yourself water line projects. A PEX cutter costs less than $20, the technique takes minutes to learn, and the result is a clean, square cut that seals the first time. Measure in place, mark your insertion depth, and use a tool made for PEX. For more hands-on plumbing skills, explore the DIY plumbing guides on this site.