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What Size Chainsaw Do I Need? Our Buying Guide

Massive chainsaw bar

Massive chainsaw bar

There are good reasons why most tree professionals have an inventory of chainsaws. They are inherently dangerous tools, and finding one you can operate safely means finding one that’s best suited for the job you need to do. The biggest, most powerful saw might be able to fell a mighty oak, but using it to cut up a fallen limb is just as dangerous as trying to use a chainsaw intended for pruning cherry trees to cut down a dead hardwood full of knots.

Whether you’re buying, renting, or borrowing, knowing what to look for in a chainsaw is an important step to completing the job safely.

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Before You Begin: Do You Need a Chainsaw?

Before you start shopping for a chainsaw, you have to answer the question: Do I need a chainsaw? Well, that depends on the work involved. Given the wide variety of landscaping tasks you might encounter, there’s a corresponding tool that’s right for the job.

Some tasks that seem like they require a chainsaw such as topping an overgrown tree or clearing some low-hanging limbs would be better off with an electric pole saw. Cutting wood at a difficult angle or anything that might contain metal calls for a reciprocating saw. And of course, there’s very little use for a chainsaw within the confines of the average wood shop – it’s an outdoor-only type of tool.

tree wood cutting with chainsaw
Image Credit: soykast, Pixabay

Chainsaw Basics

You’ll want to know a couple of the basic dimensions related to your chainsaw: the bar length and size of the engine. In both cases, larger numbers are used for bigger trees.

Bar Length

The bar is the tongue-shaped piece of metal that extends out from the engine and handle. It’s what the blade goes around when it is spinning. Bars are made in two-inch increments, starting at 12 inches and going up to 42 inches. Some tools called chainsaws have smaller bar lengths, but these are intended for only the smallest of pruning jobs. Most chainsaws intended for basic homeowner use run from 14 inches to 18, and they go up in size to the 42-inch monsters intended for professional use.

There’s a paradox when it comes to cutting length, too. An 18-inch chainsaw may or not be exactly 18 inches long and the effective cutting length of the bar is usually around 16 inches.

Chainsaw bar cutting length


When it comes to the engine that spins the blade, size matters. Engine displacements are measured in cubic centimeters (cc), and the bigger the number, the more powerful the gas engine is. Gas-powered chainsaws typically run between 30cc and 50cc, with the bigger engines designed to pair with bigger bars for the most serious work.

Gas or electric
Image credit: Kenrick Penner, Pixabay

Gas or Electric?

So far, we’re assuming that you’ll wind up with a gas-powered chainsaw. Those are the most popular and most readily available. An electric chainsaw is an option you can consider for some cases. These saws are easier to start, and because they draw their power from wall current, they’re much quieter. They are also much less powerful.

If you decide to choose an electric chainsaw, you’ll need to pick a size based on bar length. They’ll also be smaller chainsaws. If you’re looking at power output, electric chainsaws are measured in amps. A chainsaw that has a battery will measure it in volts.

Size of the Work

The biggest thing that will determine the size of the chainsaw you need is the kind of work you’re doing. A good rule of thumb is that the diameter of the trees you cut regularly should be no more than twice the length of the bar on a chainsaw. That means a 20-inch chainsaw can handle a 36-inch tree (remember, effective cutting length is roughly -2 inches of the bar length). Professional chainsaws can take that up to 2.5 times the bar length.

For most people, a quick estimate of the trees or brush you need to cut is probably more appropriate. Most people categorize things based on whether the regular cutting will be light, medium, or heavy-duty.

Chainsaws for Light Work

Light work
Image credit: Canon Eos 5D Mark III, PxHere

If you need a chainsaw for pruning limbs or cutting down saplings or small trees of the softest wood, you’ll want to get a small chainsaw. These are the chainsaws you’ll also want to use if you need to limb trees at height, because they’re the smallest and lightest, and therefore also the safest.

This kind of work is appropriate for electric chainsaws, either corded ones or ones that use batteries. Look for bar lengths of no larger than 14 inches and engines in the 30-40 cc range.

Chainsaws for Medium Cutting

Medium cutting
Image credit: Julio Olivencia Jr, U.S Department of Defense

Once you start getting into chainsaws intended to cut down trees or cut logs into firewood, you’ve moved past the ability of most electric chainsaws to work effectively. You’re also looking at bar lengths of 16-18 inches with engine displacements of 30cc to 50cc.

These are pretty ideal chainsaws to have if you’re a homeowner who has to clean up after bad storms or in the spring. They aren’t powerful enough to do a lot of work daily, but they will provide enough power to bring down the occasional tree if called for.

Chainsaws for Heavy-Duty Use

cropped man cutting a truck with chainsaw
Image Credit: bakhrom_media, Pixabay

Ranchers or people who live along the fringes of the wilderness might have a real need for bigger, more powerful chainsaws, especially if they heat with wood over the winter. They use their chainsaws a lot to bring down large hardwoods and convert them into a lot of firewood pretty quickly.

In general, these are chainsaws that have a bar length of 20-24 inches and engine displacements of 50cc to 60cc. These sizes of chainsaws are not appropriate for smaller work like pruning trees. In fact, their large bars can make them dangerous for those jobs.

Professional Grade Chainsaws

Professional grade
Image credit: Sandid, Pixabay

Chainsaws with bars between 24-42 inches and engine displacements of more than 50cc are the most savage of beasts. They’re intended for use by people with proper need and training to use them. That includes people who work on trees professionally, and some ranchers and farmers who might need to cut down large trees on a pretty frequent basis.

If you only have that kind of work to do infrequently, consider hiring a tree professional to do it. These are big, dangerous, expensive tools.

Chainsaw cutting log
Image credit: Parilov, Shutterstock

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Figuring out the size of chainsaw you need starts with knowing a little about how chainsaw sizes are determined. That means knowing what is meant by a chainsaw’s bar length and what size of chainsaw engine is going to deliver the necessary power. You’ll also want to know whether you can use an electric – either one with a cord or a cordless one driven by a battery – or need to go with gas.

Once you know these basic measurements, you can apply them to the basic kind of work you have to do. For light work like pruning, go with smaller bar lengths and smaller engines. The next step up is a good standard chainsaw with a bar smaller than 20 inches. If you’ve got heavy work, you’ll need something a little more powerful. The biggest, most powerful saws are intended for professionals and people whose lifestyles demand they do frequent, heavy-duty cutting.

Featured Image Credit: Parilov, Shutterstock

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