How Big of a Chainsaw Do I Need? Bar Length and Engine Size Chart

Match the chainsaw’s bar length to the diameter of the thickest wood you’ll regularly cut, then match the engine size to that bar – not the other way around. A bar about 2 inches longer than your biggest logs gives you enough reach to cut through in one pass without maxing out the tip, and the engine needs enough displacement (cc) to keep that longer chain moving at full speed. A bigger saw than you need isn’t a safety margin; it’s more weight to control and more fatigue over a cutting session.

Most homeowners overbuy on bar length and underthink engine size, which is backwards for both cost and safety. Below is a quick-reference chart by job type, followed by the actual rule chainsaws are sized by, why an oversized bar increases kickback risk instead of reducing it, and the safety gear that matters more than horsepower.

Chainsaw Size By Job: Quick-Reference Chart

These are real-world tiers based on typical engine displacement (cc) and bar length pairings sold for each use case – not maximum theoretical cutting capacity.

Job Type	Engine Size	Bar Length
Light limbing, pruning, small yard cleanup	~30-40cc	10-14 inches
General homeowner: firewood, felling small-to-medium trees	~40-50cc	14-18 inches
Larger felling, bucking big logs, professional/frequent use	50cc or more	18 inches or more

If most of what you cut is under 12 inches across – typical split firewood rounds and yard trees – the middle tier covers nearly everything you’ll run into without the extra weight of a saw built for full-size felling.

The Bar-To-Diameter Rule (And Why Engine Size Has To Match)

The starting point for sizing is simple: measure the bar length you’d need as roughly 2 inches longer than the diameter of the thickest wood you cut regularly. That extra length lets the tip clear the far side of the log in a single pass instead of you sawing partway through and flipping the log to finish the cut from the other side.

Bar length alone isn’t the whole story, though. A longer bar carries more chain, and that chain needs enough engine power behind it to keep full cutting speed under load – a saw that’s underpowered for its own bar bogs down mid-cut and stalls, which is its own hazard. As a rough guide, each additional 2 inches of bar length calls for about 5 to 10cc more engine displacement to keep pace. That’s why a 20-inch bar shows up on 50-60cc saws, not on the same 38-40cc engines that run a 16-inch bar comfortably.

Why Bigger Isn’t Automatically Better: Kickback Risk

The upper quadrant of the bar’s tip is the real danger zone on any chainsaw – when that specific area touches wood, a branch, or anything else, the chain’s own momentum can snap the whole saw back and up toward the operator faster than a human reaction can counter it. That’s kickback, and it’s the mechanism behind most serious chainsaw injuries, not dull chains or user error alone.

Oversizing your saw makes this worse, not better. A longer bar means more of that tip zone is in play during everyday cuts, and a heavier saw is harder to keep braced and under control if kickback does happen. Many current saws use a reduced-kickback bar – a narrower nose radius that shrinks the danger zone – and pairing that with the smallest bar that comfortably handles your actual wood, per the cutting-capacity numbers for your bar length, does more for real-world safety than buying extra inches “just in case.”

Gas, Battery, Or Corded Electric?

Power source affects how a given bar-and-engine combination actually feels to run:

• Gas: Still the standard for anything in the 16-inch-and-up range – unrestricted by cord or battery runtime, and the most power per pound. Needs mixed fuel, regular carb/air-filter maintenance, and is the loudest, heaviest option.
• Battery: Closed the performance gap significantly on 14-16 inch saws in the last couple of years – enough torque for most homeowner firewood work, instant start, no exhaust fumes. Runtime and battery cost are the tradeoffs on longer sessions.
• Corded electric: Fine for light pruning and small branches near an outlet, but the cord limits where you can work and these rarely run bars over 14-16 inches.

Essential Safety Gear Before You Pull The Cord

The saw’s size matters less than what you’re wearing when something goes wrong. A real safety loadout for any chainsaw, regardless of bar length:

• Chainsaw chaps: Built from ballistic fibers that pull loose and jam the drive sprocket within a fraction of a chain rotation if the moving chain touches them – they need to stay clean and unmatted to work as designed.
• Helmet with a mesh or polycarbonate visor: Protects against kickback impact and flying debris at the same time.
• Ear protection: Chainsaws run well past safe long-term exposure levels; muffs or plugs are not optional for regular use.
• Cut-resistant gloves and sturdy boots: Gloves protect grip hand and vibration exposure; boots need real ankle support and ideally a reinforced toe.

Keep both hands on the handles at all times, plant your feet before you start the cut, and never reach a saw out at arm’s length – a chainsaw is controlled with your whole stance, not just your grip. If you’re new to a saw larger than what you’ve used before, run a few practice cuts on a stable, supported log before tackling anything at height or under tension.

Frequently Asked Questions On How Big Of A Chainsaw Do I Need

How Big Of A Tree Can A 20 Inch Chainsaw Cut?

A 20-inch bar can fell trees up to about 40 inches in diameter by cutting from both sides and meeting in the middle, though a single clean pass tops out around the bar’s own length. A 20-inch saw is typically paired with a 50cc-plus engine to keep that much chain moving at full speed, so it’s sized for medium-to-large felling and bucking, not everyday yard work.

Should I Get A 14 Or 16 Inch Chainsaw?

Go by the thickest wood you’ll actually cut on a regular basis, plus about 2 inches. A 14-inch bar covers pruning, small branches, and firewood rounds under about 12 inches across. A 16-inch bar adds margin for slightly larger trees and logs without jumping up to a heavier engine class – it’s the more versatile choice for most homeowners who don’t know exactly what they’ll be cutting a year from now.

What Is A Good Size Chainsaw For Home Use?

For most homeowners, a 14-16 inch bar on a 35-45cc engine covers pruning, firewood, and storm cleanup without the extra weight of a felling-class saw. Match the exact bar to the wood you cut most often using the 2-inch rule above, prioritize a model with an inertia-activated chain brake, and don’t buy more saw than you can comfortably hold up for a full cutting session.

Is A 16, 18, Or 20 Inch Chainsaw Better?

Neither is “better” outright – each is sized for a different job. A 16-inch saw handles average yard trees and firewood with the least weight and easiest control. An 18-inch chainsaw is a good middle ground, offering more reach for occasional larger logs without a big jump in engine size – see our full 16-inch vs 18-inch comparison for the exact cutting-capacity difference. A 20-inch saw only makes sense once you’re regularly felling or bucking trees in the 30-40 inch diameter range, since it needs the engine power (and the operator experience) to match.

Conclusion

Size a chainsaw from the wood up: measure the thickest logs or trunks you’ll regularly cut, add about 2 inches for your bar length, then pick an engine with enough cc to keep that bar’s chain running at full speed. Pair whatever you land on with real chaps, eye and ear protection, and a two-handed, feet-planted stance, and you’ll get more safety benefit than any amount of extra bar length alone provides.