How Thick a Branch Can a Hedge Trimmer Cut? Blade Gap Explained

Most domestic hedge trimmers will cut branches up to the size of their blade gap, which is usually somewhere between 15mm and 26mm. In practice, comfortable everyday cutting happens at roughly two thirds of that figure, so a trimmer rated at 20mm is happiest on stems around 12mm to 14mm. Anything thicker belongs to loppers or a pruning saw, and pushing past the limit is how blades get bent and gearboxes get cooked.

What the blade gap actually tells you

Every hedge trimmer has a row of teeth with a set distance between them. That distance is the blade gap, sometimes listed as tooth spacing or cutting capacity. It is a physical limit: if a stem does not fit between two teeth, the blades cannot close on it and the tool simply chatters or jams.

Manufacturers publish that gap as the headline cutting capacity, which is where the confusion starts. The number is the maximum a stem can measure and still physically enter the blade, not a promise that the motor will slice through green wood at that size all afternoon. A cordless trimmer with a 22mm gap might manage the odd 20mm stem, but feed it a hedge full of them and you will hear the motor bog down within minutes.

Realistic cutting sizes by trimmer type

• Light corded and battery trimmers (15mm to 18mm gap): comfortable up to about 10mm. Fine for privet, box, conifer and annual growth on beech or laurel.
• Mid range cordless trimmers (20mm to 22mm gap): comfortable up to roughly 12mm to 14mm, with occasional thicker stems taken slowly.
• Petrol and pro grade trimmers (26mm to 34mm gap): genuinely handle 18mm to 20mm stems, and will chew through neglected hedges that stall domestic machines.

Wood type shifts these numbers too. Fresh conifer or laurel growth is soft and cuts easily. Old hawthorn, blackthorn or a woody privet base is dense and dry, and a 12mm stem of that behaves more like an 18mm stem of soft growth.

Why exceeding the limit damages the tool

Hedge trimmer blades are thin, hardened steel designed for shear cuts on soft growth. Force them onto oversized wood and three things go wrong. The blade tips can bend or snap, which throws the two bars out of alignment and ruins the shearing action. The gearbox takes the shock load, and on cheaper trimmers the drive gear is plastic or soft alloy. Motors overheat when they sit under stalled load, and on cordless models that drains a battery in a fraction of the usual runtime.

The other cost is the hedge itself. A trimmer that cannot make a clean cut leaves crushed and torn stems. Those wounds heal slowly and are an easy entry point for disease, which is why a torn laurel hedge often shows browning tips a few weeks after a hard trim.

How to handle stems that are too thick

1. Walk the hedge first. Spend two minutes spotting the thick stems before you start. Most hedges have only a handful.
2. Cut them out by hand. Bypass loppers handle anything up to roughly 30mm to 40mm. A folding pruning saw covers the rest.
3. Take thick growth back below the finished line. Cut a few centimetres lower than where you want the hedge face so the trimmer never touches those stumps.
4. Then shape with the trimmer. With the oversized wood gone, the trimmer only meets growth it was designed for.

For a badly overgrown hedge, this reversed order saves a huge amount of time and stops you fighting the tool for an hour.

Technique that stretches your effective capacity

You can cut slightly thicker material safely by changing how you present the blade. Approach thick stems side on rather than head on, so the teeth get a scissor action instead of a chopping one. Move the trimmer slowly along the stem rather than pressing straight in, which lets the reciprocating blades take repeated bites. Keep the blade square to the branch, since an angled cut has more material to shear through.

Sharpness matters just as much as spec. Blades that have been dulled by grit or a season of hedge dust lose a large chunk of their practical capacity, and a well maintained 18mm trimmer will out cut a neglected 22mm one. Cleaning off sap and applying a light resin solvent after each use keeps the blades sliding freely.

Choosing a trimmer for thicker work

If your hedges are mature hawthorn, laurel or an old mixed boundary, buy for capacity rather than for length. A 20mm gap or larger is a sensible floor. Also look at blade length: 60cm and above gives you a longer stroke and more leverage per pass, though it makes detail work harder. Battery voltage on cordless models is a rough proxy for torque, so a 36V or 40V machine will hold speed under load far better than an 18V one.

Anyone cutting genuinely woody material regularly should consider a pruning saw attachment or a small chainsaw instead. A hedge trimmer is a shaping tool, and treating it as a general purpose cutter is the fastest way to shorten its life.