What Size Chainsaw Do You Need?

Bar length is the number that answers the buying question; power and weight follow from it.

• Bar length is the number on the box: 14, 16, 18 or 20 inches. This is the size that matters.
• Power is engine size in cc for gas, the motor and battery platform for cordless, and amps for a corded saw. It is what keeps the chain moving through the bar.
• Overall length and weight decide whether you can hold the saw for an hour without your arms shaking.

These three are linked. A longer bar needs more power to hold chain speed, more power means more weight, and weight is what limits how long you can work safely. That chain is the spine of every sizing decision.

Bar length is also capped by the powerhead. A longer bar will physically bolt onto a small saw, but the engine or motor will not pull it properly. The chain slows in the cut, the saw bogs down, and you end up forcing it. Buy the bar the powerhead was built for.

The near-universal rule of thumb is a bar about two inches longer than the wood you cut most often. The gap exists for a reason most shoppers never hear: the number on the bar is not the cutting length.

A 16-inch bar has roughly 14 inches of usable cutting length. A 20-inch bar cuts about 18 inches. The two-inch allowance is what makes the called length line up with the wood in front of you.

There is a practical limit on going long. Don't pick a bar so long that the tip is likely to hit the ground or another branch while you cut. Kickback comes from the bar tip, and a tip that touches something solid is how it starts.

You can get through wood wider than your bar with a cut from each side. That is a technique for someone with experience, not a reason to buy a saw that is too small for your regular work.

Five minutes with a tape measure before you shop settles the question better than any chart.

1. Measure the wood. Find the diameter of the thickest piece you cut regularly: firewood rounds, storm limbs, the trunks you actually buck. Not the biggest tree you have ever seen in the yard.
2. Measure a bar if you are unsure what a size feels like. Run the tape from where the bar leaves the housing to the tip, then round to the nearest even number.
3. Write the number down before you open a product page, and match it to the table below.

Most buyers skip this step and shop by the size they remember a neighbor using. The tape takes the guesswork out.

16 inches is the most-recommended single size for homeowners, and 20 inches is the ceiling.

Size is bar length plus the power that pulls it, and each power source is sized on its own scale.

Gas saws are sized in cubic centimeters

Gas saws under about 62 cc are the homeowner class; larger is professional. Consumer saws ship with a low-kickback chain. The rough bands run 30-35 cc for light duty, 36-41 cc for medium work, 42-50 cc for heavy duty and firewood, and 50 cc and up for professional use.

Battery saws are not sized by volts alone

Voltage labels are marketing. A pack sold as 20 V Max is 18 V nominal, and a 40 V Max pack is 36 V nominal. The real spec is the bar the maker pairs with the motor and the maker's printed log rating. Broadly, 18-20 V covers limbing and pruning, 40 V covers storm cleanup and light firewood, and 56-80 V is where cordless matches a 40 cc gas saw cut for cut.

Amp-hours decide cuts per charge. Expect roughly 30-40 minutes of semi-continuous cutting and about an hour to recharge, so plan on a second pack if you have a full day of work.

Corded saws are sized in amps and distance

A corded saw runs a motor of about 8-15 A and typically carries a 14-16 inch bar. The sizing question here is really a distance question: you are limited to roughly 100 feet from an outdoor outlet, on a heavy-gauge extension cord, and you can't use one in wet weather.

Published weight is the powerhead only. Add roughly 1.5-2 lb for the bar and chain, about a pound for a pint of fuel, and the battery weight on a cordless saw. Shoppers comparing dry weight numbers are comparing incomplete figures.

Fatigue is the real limit. Most chainsaw injuries happen late in the day, when tiredness sets in. The right upper limit is the weight you can work with for several hours, not the most you can lift once. A bigger saw is a heavier saw, and a heavier saw is one you hold wrong, cut above shoulder height with, or stop using altogether.

The safety basics apply at any size:

• Kickback comes from the bar tip, so keep the tip clear of wood, ground and branches.
• Use the chain brake and check that it engages before every session.
• Wear leg protection, since most chainsaw injuries are to the legs, and hearing protection, since every saw runs above 85 dB.
• Never cut above shoulder height, never from a ladder, and never one-handed.
• Never run a gas saw indoors.

Three sizes sit outside the main table, and each has a clear owner.

Mini and one-hand pruning saws

A 6-inch bar cuts about 4 inches; an 8-inch bar cuts about 6 inches. On some models a tip guard means only part of that bar is usable. These saws are for pruning, limbing and kindling, not for felling or firewood. Despite the one-hand label, the safe technique is still two hands.

Top-handle saws

These are arborist tools for working aloft in a harness. On the ground they raise kickback risk because you lack the leverage of a rear-handle saw. A homeowner doing ground work does not need one.

Pole saws

For limbs overhead, the answer is not a longer chainsaw bar but a pole saw. Bars run 6-12 inches, with 8 inches the most common, and the bar should be about two inches longer than the branch. Reach is typically 8-12 feet of working height. Never use one near power lines.

Some jobs are faster, safer and cheaper without a chainsaw, and knowing which ones saves a return.

• Branches under about two inches come off faster with loppers or a hand saw.
• Limbs overhead call for a pole saw, not a chainsaw on a ladder.
• A trunk too big for a 20-inch bar, or anything near a structure or a power line, is a job for an arborist.
• A one-off storm cleanup may be covered by a smaller saw or a borrowed one.

Bar length and power class are the biggest drivers. A 20-inch 50 cc saw costs more than a 14-inch 35 cc saw because there is more engine, more bar and more weight in it.

Power source shifts the cost structure. Corded saws are the simplest and least expensive to build. Battery saws move cost into the battery platform, and a spare pack is a real line item. Gas saws carry engine cost plus fuel and maintenance.

Build class shows up too. Consumer and professional saws differ in metal versus plastic components, serviceability and how the saw is put together.

Each tier brings something different:

• Entry tier: a light saw for limbing and small cleanup.
• Mid tier: the 16-18 inch homeowner saw that handles firewood and storm work.
• Top of the homeowner range: a 20-inch saw with the power to match, at a weight you will notice by the end of the day.