A string trimmer gets into places that a lawn mower can’t. It’s the ideal tool for keeping the edges of your garden or walkway neat and tidy and for manicuring around fence poles and tree trunks. It can tackle tall grass and weeds, too, which might bog down a regular lawn mower.
String trimmers—which are also sometimes referred to by popular brand names including Weed Whackers or Weed Eaters—have either a curved or straight shaft, and typically run on either gasoline or lithium-ion battery. A small number of models are corded, with cords that are only a foot long, so you'll want an extension cord that's at least 50 to 100 feet in length to plug into.
Take note that electrics are both better for the earth and have improved exponentially in how well they perform in recent years. Below, we delve into these and other factors you should consider when you shop for a string trimmer.
How We Test String Trimmers
In our tests, we use each trimmer to tackle typical yard weeds and high grass as well as dense brush, noting and timing how long each model takes to clear a defined path. We also test each model at edging, or its ability to create a neat and straight line along a walkway. And we look at how easy each model is to hold, maneuver, and operate, noting how difficult it is to start up or feed extra line through the cutting head.
We test gas and electric models with curved and straight shafts. If you’ve never used a string trimmer, try out curved-shaft and straight-shaft models in a home center or hardware store to see which feels better.
To see how well the string trimmers in our tests perform, see our string trimmer ratings.
Curved or Straight Shaft?
The straight- vs. curved-shaft debate in terms of handling is largely one of preference: Shorter curved shafts allow the user to nimbly maneuver around obstacles, while straight-shaft tools (which are generally longer) increase the user's reach and coverage from a given point. In general, pros favor straight-shaft models for this reason—you can cover more ground with fewer steps.
Which Power Source Is Right for You?
A string trimmer can be powered by gasoline, a battery, or a power cord.
"In our tests we find that corded, battery, and gas-powered string trimmers can all cut well, depending on the model," says Misha Kollontai, CR's engineer in charge of string trimmer testing. "The choice between power sources should really be dictated by the size and layout of your yard."
Corded electric string trimmers are best for yards up to about 1/4 acre. Battery-powered trimmers are good for a yard up to about a 1/2 acre, and they can tackle much larger yards if you have multiple batteries that you can charge and swap in. Gasoline string trimmers work for a yard of any size.
Other Considerations
Should You Buy a Powered Base?
With gas string trimmers, you’ll have the option of buying a stand-alone tool or a powered base, also known as a split shaft. A powered base or split shaft is basically an engine designed to accept different attachments, and it’s typically sold with a string trimmer head. For most models, you can also get a hedge trimmer, a pole saw, an edger, and a brush cutter, and even a cultivator attachment. It’s a good option if you need a string trimmer and any or all of the additional tools, and you don’t want to buy each separately.
Mind the Gap
Before you buy any string trimmer, look at the cutting head, where it meets the shaft of the trimmer. If there’s a large gap, be warned that tall grass will probably get wrapped around the shaft in that spot. Instead, look for a model with a minimal gap, or one with an easy-to-remove cutting head so that you can quickly pop the head off and get rid of weeds.
Safety First
String trimmers can easily break through skin and send debris flying while they cut. They have a shield to deflect most debris, but even so, you’ll want to wear gloves, protective eyewear, boots, and long pants, in addition to hearing protection for gas models.
String Trimmer Types
Let your lawn and landscape dictate which type of string trimmer you buy.
Gas-Powered String Trimmer
Traditionally the best choice for large properties, a gas-powered string trimmer goes anywhere and can run indefinitely. This type is also popular, so you’ll have plenty of options when shopping if you go this route—just not as many as with battery models, which is now the most popular style. Look for models with an adjustable handle and a translucent gas tank so that you can see when fuel is low. Models with a four-cycle engine run cleaner and use regular gas but cost more. Models with a two-cycle engine cost less, but you’ll need to add oil to your gasoline. All the gas-powered string trimmers in our tests are loud enough to require hearing protection for the user.
Cost: $70 to $330
Corded-Electric String Trimmer
Though corded yard tools may seem outdated, a corded string trimmer can perform really well for a certain subset of homeowners. If you have a small yard and don’t need to trim more than 100 feet from an outlet, these are ideal. Most have a short cord and require a long outdoor-rated extension cord—you can typically find these cords in lengths up to 100 feet. Corded-electric string trimmers tend to be the cheapest, plus they start instantly and run indefinitely, and you don’t need to worry about buying gas or charging a battery.
Cost: $50 to $70
Battery-Powered String Trimmer
In our latest tests, the best battery-powered models trim as well as or even better than gas models. Plus they produce no emissions and run quietly. They also start instantly every time, without you having to fuss over the choke or yank a pull-cord. They require far less maintenance, and their batteries can typically be used in other outdoor power tools from the same brand, including lawn mowers, hedge trimmers, leaf blowers, and chainsaws. The life span of the lithium-ion batteries used to power these tools is still a big unknown, so look for a long warranty that specifically applies to the battery. Expect to cut for about 30 minutes on a single charge. Most batteries take about an hour to recharge once they've fully drained.
Cost: $70 to $300
More to Consider When Shopping for a String Trimmer
Shopping for a string trimmer can be confusing. Here’s the help you need to get the job done.
Straight vs. Curved Shaft
The shaft transfers power from the engine or motor to the lines that do the cutting. Models with a straight shaft offer a longer reach, and they tend to be better for tall users and for reaching beneath bushes and other shrubs. Models with a curved shaft (shown) tend to be lighter and easier to handle.
Rotating Head
On some models, the cutting head can be swiveled to a vertical position for edging. This feature is especially useful because the trimmer can otherwise feel unwieldy if you have to maneuver it 90 degrees—and hold that position—for several steps as you edge your lawn where it meets a driveway or sidewalk.
Cutting Line
All manufacturers tell you which size replacement line fits your trimmer. Be sure to use what’s intended for your trimmer. Line that’s too thin can compromise cutting power, while line that’s too thick can bog down a trimmer’s engine or motor. Trimmers with two lines cut more grass with each revolution than single-line models, so they can typically handle heavier growth.
Cutting Line Feed Options: Bump Feed, Fixed Line, and Auto Feed
A bump-feed releases line from a spool when you bump the trimmer’s head on the ground, but more models are using fixed-line heads with short lengths of line to help eliminate the jams and tangles associated with loading new line. You thread in a piece of line as needed—though you’ll have to do that relatively frequently. Fixed-line heads are also available as aftermarket items. Auto-feed heads come pre-wound and release line on their own as needed.
Starting Aids and Stop Switches
Spring-assisted starting makes pulling the starter cord of a gas-powered trimmer easier. And a relatively foolproof sequence of pushing the fuel-primer bulb and engaging the choke delivers the proper fuel mixture to a cold engine for faster starts. Trimmers that have the stop switch within easy reach let you quickly stop the engine or motor if you need to.