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If you want your yard done without yanking a starter cord, 40V cordless trimmers are the simplest answer — and the trick is picking the right cutting width and battery for the size of your lot. Buy too narrow and you make twice the passes. Buy too heavy and your shoulders quit before the weeds do. This guide sorts the real trade-offs so you can pick once and stop thinking about it.
I’m Min — the founder and writer behind Gadgets Feed. This guide is built by comparing the manufacturers’ published specifications and the patterns across verified customer reviews, so you get each pick’s real strengths and trade-offs instead of marketing spin.
Weed eating stops being a chore once the tool actually matches your yard, so here is what separates the genuinely useful 40v trimmer from the one that sits in the garage.
Our Picks at a Glance
How To Choose The Best 40V Trimmer
The most common mistake is assuming higher voltage means more cutting power. Voltage tells you the battery platform’s muscle, but the motor type, cutting width, and line thickness do the actual work in your flower bed.
Cutting Width Decides Your Pass Count
A wider swath means fewer passes along the fence line. A 17-inch trimmer covers more ground per pass than a 13-inch model, which matters most if you have long stretches of edging. Narrower heads like 12 inches steer easier around garden beds and tight corners.
Brushless Versus Brushed Motors
A brushless motor has fewer rubbing parts, so it runs cooler and lasts longer than a brushed one. If you trim weekly, brushless is worth the extra cost because it holds RPM when the grass gets thick.
String Feed And Line Diameter
Bump feed lets you tap the head on the ground to release fresh line, while auto-feed pulls line as you work. Thicker line like 0.095-inch stands up to heavy weeds better than thin line, but it demands more motor power.
Quick Comparison
| Model | Best For | Cutting Width | Weight | Battery Included | Amazon |
|---|---|---|---|---|---|
| BLACK+DECKER 40V MAX 13 in String Trimmer (LST136)★ Best Overall | Suburban lawn upkeep on one charge | 13 inches | 7.8 pounds | 2.0Ah, included | Amazon |
| RB 17″ 40V Cordless String TrimmerWidest Swath | Wide swath and heavy-weeds bulk clearing | 17 inches | 6.6 pounds | 2.0Ah, included | Amazon |
| DongCheng 40V Brushless String TrimmerLongest Runtime | Long runtime on a two-battery system | 15 inches | 7.3 pounds | Two 4.0Ah, included | Amazon |
| RYOBI 40V Attachment Capable 15″ Trimmer Bare Tool | Adding to an existing RYOBI battery collection | 13 inches | 11 pounds | Not included | Amazon |
| HART 40-Volt 12″ String Trimmer | Budget trimming for mulch beds and fence lines | 12 inches | 7 pounds | Not included | Amazon |
| RYOBI 40V HP Brushless Whisper Series 17 in. | Quiet operation with a carbon fiber shaft | 17 inches | 12 pounds | Not included | Amazon |
| Kobalt 40-Volt Max 15-in Straight Trimmer | Wide swath with a 4.0Ah battery in the box | 15 inches | 16.1 pounds | 4.0Ah, included | Amazon |
| SKIL PWR CORE 40 Brushless Multi-Head System | Building a multi-tool yard system | 16 inches | 14.5 pounds | 4.0Ah, included | Amazon |
| Worx Cordless String Trimmer WG186 | Attachment-capable trimming with two batteries | 15 inches | 11.9 pounds | Two 4.0Ah, included | Amazon |
| RYOBI 16″ Carbon Fiber Shaft String Trimmer | Brush clearing with over 45 minutes of runtime | 12 inches | 12 pounds | Not included | Amazon |
| Greenworks 40V 16 in Cordless String Trimmer | Large yards with swappable attachments | 16 inches | 15.2 pounds | 4.0Ah, included | Amazon |
In‑Depth Reviews
1. BLACK+DECKER 40V MAX 13 in String Trimmer Edger Cordless (LST136)
Our pick — over 4★ from 8,000+ verified ratings; the strongest balance of quality and price.
The yard-work veteran that flips from trimmer to edger in seconds without a single tool.
For the homeowner with a normal suburban lot, this is the safest bet on the list. It spins up to 8500 RPM — the fastest cutting speed here — which is why it slices through established grass without bogging down. That speed beats the DongCheng’s 6000 RPM, so thick patches clear noticeably quicker.
The PowerCommand dial is the feature people lean on most: you pick between maximum power for thick weeds or maximum runtime for long stretches, so a light trim doesn’t burn the battery you need for the fenceline. The automatic feed spool (AFS) pushes out fresh line on its own, which means no bumping the head against the ground all afternoon.
You get everything you need to start trimming right away: the trimmer, a 40V 2.0Ah lithium-ion battery (a rechargeable battery that holds its charge for months), a fast charger that refills the pack in 2 hours or less, and a 2-in-1 conversion that turns it into an edger. What wins people over is how light it feels in hand compared to gas units — the weight is the most-discussed trait, and rightly so, because a 7.8-pound tool you can carry for a full session gets used more often. That 7.8 pounds does run above the RB’s 6.6 pounds, so if you want the lighter carry, the RB above wins on that one number.
The honest catch is the string. Some owners find the line breaks mid-job, and you have to wind it tightly and evenly or the feed jams up. There’s also the occasional bundle mix-up where a slower charger shows up instead of the fast one, so double-check what’s in the box before you head out.
What It Gets Right
- 8500 RPM cutting speed — the fastest in this lineup
- 2-in-1 trimmer-to-edger swap with no tools needed
- 2-hour fast charge refills the battery quickly
- Light 7.8-pound build that’s easy to carry for a full session
Where It Needs Care
- Line can break mid-use if not wound tightly
- Some bundles ship with a slower charger than advertised
- A few buyers report a battery failing early
Best for: the suburban homeowner who wants one tool that trims the lawn and cleans up the driveway edges.
Think twice if: you have half an acre or more of heavy growth — this shines on standard-sized lots, not acreage.
2. RB 17″ 40V Cordless String Trimmer with 2Ah Battery & Charger
A 17-inch swath that clears ground faster than almost anything else on this page.
If your trimming session is mostly about covering distance, this is the pick. Its 17-inch cutting width is the widest tied for first here, and it beats the BLACK+DECKER’s 13 inches by a wide margin — 31% wider, to be exact. That means fewer passes along the fence and a shorter afternoon overall.
The line is the other reason to look here. That 0.095-inch heavy-duty dual line stands up to thick brush without snapping constantly, which is the difference between a smooth run and a stop-and-restring break every few minutes. Owners describe it — in their words — as cutting through thick vegetation “like a beast,” and the consensus is that it handles tough weeds and thick grass with ease.
What people rave about beyond the power is the handling. It’s relatively quiet, low-vibration thanks to an anti-vibration handle, and light enough that your hands aren’t buzzing after a session. A 2.0Ah battery and charger come in the box, along with four rolls of spare line.
The battery reality check: runtime is the most-discussed trade-off here — owners find the pack cuts more than their previous trimmers but note it isn’t generous. Run it on the eco setting for light work and you’ll stretch it further.
Assembly gripes: getting the handle and rubber collar mounted is fiddly, and a few people find the handle slips a touch until it’s seated right.
Reach for this if: you value a wide, fast pass and thick line that survives heavy weeds.
Look elsewhere if: you want a dead-simple setup from the start — the assembly takes some patience.
3. DongCheng 40V Brushless Cordless String Trimmer, 15-Inch Weed Wacker
Two batteries in the box and up to 45 minutes of run time before you reach for a charger.
Runtime is the whole story here. This trimmer pairs two 20V 4.0Ah batteries to deliver 40V of output, and that combination gets you up to 45 minutes of trimming on the low setting. The brushless motor runs cooler and holds speed, which is why it can keep cutting thick grass without slowing. It tops out at 6000 RPM, a step below the BLACK+DECKER’s 8500 RPM, so it’s more about stamina than raw speed.
A 1-hour recharge gets you back to work fast, and because both batteries share DongCheng’s 20V platform, they run that brand’s other tools too. Buyers using it on a small tree farm report one battery set finishing all their trimming alongside an 18-inch chainsaw.
There’s a real weight trade-off, though. Add both batteries and the unit climbs toward 14 pounds, which is heavy for a full session — a strap helps. The head angle also can’t be adjusted, so edging takes more wrist work.
The balance sheet: owners call this “Makita quality, Ryobi price” and appreciate the easy line loading, but some point to a flimsy-feeling handle and batteries that don’t cross over to their other brand’s tools.
Made for: people who want long runtime and a second battery included without paying a big-brand premium.
Skip if: a 14-pound loaded weight would tire your arms — this one benefits from a shoulder strap.
4. RYOBI 40V Attachment Capable 15″ String Trimmer Bare Tool
A bare tool for the RYOBI owner who already has the batteries and wants up to 71 minutes of cutting.
This is a battery-platform play. It’s sold as a bare tool, meaning no battery or charger in the box, so it only makes sense if you’re already stocked up on RYOBI 40V packs. With a 40V 4Ah battery it runs up to 71 minutes, and using the EXPAND-IT system you can swap the trimmer head for other attachments to save space and money over buying separate tools.
If battery compatibility is the reason you’re here, this is the RYOBI pick — but pair it with the right cell. The reality is that this unit has drawn heat over overheating, with reports of motors smoking or melting under hard use. Treat it as a light-to-medium duty trimmer, let it rest instead of powering through a jungle, and it holds up fine for routine lawn edges.
Reasons To Buy It
- Up to 71 minutes of runtime with a 40V 4Ah battery
- EXPAND-IT compatible so one power head drives multiple attachments
- More cutting power than a 21cc gas trimmer per the maker’s claim
Reasons To Pause
- Battery and charger are sold separately
- Overheating has been a recurring concern — give it breaks
Suits: existing RYOBI 40V owners who want an attachment-capable head without paying for another battery.
Not for: anyone starting fresh or with heavy, prolonged brush clearing.
5. HART 40-Volt 12″ String Trimmer (Tool Only)
A featherweight tile trimmer for mulch beds and fence lines that won’t wear out your arms.
At 12 inches it’s the narrowest cutting width on the list, which makes it nimble around flower beds and tight corners rather than a fast lane-clearer. It uses.080-inch line and an auto-feed head that dispenses line as you go. The upside to that slim profile is light weight and easy maneuvering in areas where a wide trimmer feels clumsy.
Here’s the part that catches people: this is a bare tool. No battery, no charger. Buyers love the trimmer itself — one reports running twice weekly on an acre for six years on a single charge — but a couple of shoppers felt misled expecting a battery in the box. Just make sure you already own HART 40V batteries and chargers before you order.
What it does well: the light weight and easy assembly win people over, and the runtime and string hold up for regular use.
The recurring caveat: motor reliability is the most-discussed concern, with a few owners reporting the motor smoking or burning out — treat it as a light-duty tool.
Ideal for: HART 40V owners who want a light, maneuverable trimmer for beds and edges.
Move on if: you need a battery included or a tool that handles heavy, prolonged cutting.
6. RYOBI 40V HP Brushless Whisper Series 17 in. Carbon Fiber Shaft Trimmer (Tool Only)
A carbon fiber shaft and a 17-inch head built to cut down the noise along with the weeds.
Make no mistake: this is a bare tool for the RYOBI 40V household. The draw here is the 17-inch cutting width and the Whisper Series design, which puts the focus on keeping the decibels down while a brushless HP motor does the work. The carbon fiber shaft cuts the weight of the tool in a spot where it counts, so a long trim session feels less like a workout.
For power, owners are vocal about the trigger response and the reserve it holds — plenty of muscle for a home lawn, which is exactly its lane. The control trigger lets you moderate speeds so light work sips the battery.
One assembly note: a few units have shipped without the hex screws for the folding joint, so it’s worth checking the box before you plan a session. The performance itself, though, is what keeps owners recommending it.
The honest fit: this is a homeowner-grade trimmer with pro-grade feel — ample power for suburban yards, not a commercial brush hog.
Order the battery: it’s tool-only, so pair it with a RYOBI 40V pack or it won’t run.
Buy it if: you already run RYOBI 40V batteries and want a quiet, wide-swath trimmer.
Pass if: you need everything in one box — no battery here.
7. Kobalt 40-Volt Max 15-in Straight Cordless String Trimmer (4ah Battery and Charger Included)
A 15-inch brushless trimmer with a big 4.0Ah battery that shoulders the run time so you don’t babysit the charge.
The headline here is the battery in the box. That 4.0Ah lithium-ion pack is a big cell — described by owners as four times the size of a typical 20V battery — and it’s the reason this trimmer can run a full yard without swapping. A brushless motor drives the 15-inch swath, and a variable-speed trigger lets you dial the cut in around edges and obstacles without nicking the fence.
In practice, the swath is generous: 15 inches clears more per pass than the BLACK+DECKER’s 13-inch head. Owners coming from a 2-stroke weedeater say it replaces gas duty well — thick 24-inch grass needs the higher setting, and the lowest setting stays controllable.
Weighing in at 16.1 pounds, this is the heaviest unit on the list, so plan on a strap or shorter sessions. There’s also the expected scatter of shipping mishaps and one rough review, but the general read is a sturdy, precise cut.
Standout: that 4.0Ah battery and the variable-speed trigger make this a capable, gassed-up cordless replacement for small yards.
Plan for: the weight — 16.1 pounds is a lot to carry, and a strap is worth having.
Best for: the buyer who wants a big battery included and a wide brushless cut without going gas.
Think twice if: your arms flag with heavy tools — this is the heaviest trimmer here.
8. SKIL PWR CORE 40 Brushless 40V Multi-Head System, 16-Inch String Trimmer Kit
A 16-inch brushless trimmer that doubles as the base for a full set of yard attachments.
If you’ve ever been annoyed by buying five separate tools, this Multi-Head System is the pick. It’s a power head first — the 16-inch string trimmer you see here — but the same unit accepts SKIL 40V attachments for other yard tasks, and owners mention their existing attachments drop right on. The digital brushless motor keeps the 16-inch swath spinning efficiently, and dual-line bump feed releases line with a quick tap on flat ground.
Battery tech is where SKIL puts effort. The PWR CORE 40 4.0Ah pack wraps each cell in cooling material, which the maker says delivers 25% longer runtime and double the battery life, and the included Auto PWR JUMP charger tops it up fast. Customers note about 45 minutes of run time per charge, which is generous for a big yard.
The trade-off is weight. With a large battery on board this trimmer gets heavy — owners note it turns into a workout, and some add a shoulder strap to cope. The Twist Load head and two-speed selector help you manage it, but if you want featherweight, look elsewhere.
The real pitch: one power head, many attachments — this is a system, not just a trimmer, and it clears hefty weeds well.
The trade: the big battery is heavy on the trimmer, so a strap helps — smaller platform batteries lighten the load.
Perfect for: homeowners who want one power head to drive a whole set of SKIL yard attachments.
Skip if: you’re after a light, quick grab-and-go trimmer.
9. Worx Cordless String Trimmer, 40V 15″ Electric Weed Wacker, WG186
Two batteries in the box and a split-shaft head that takes DriveShare attachments for the rest of the yard.
Worx leans hard into “gas-like power” here, and the 6000 RPM no-load speed with a brushless motor backs that up for tall grass and weeds. A variable-speed 15-inch dual-exit head — with an easy-load trimmer head and a bonus replacement head included — makes string changes quick. On top of the trimming, the split shaft accepts DriveShare attachments, and Worx says it fits most other attachment-capable systems.
The value angle is the battery kit: you get two 4.0Ah Power Share Pro batteries and a dual-slot charger in the box, which spreads the run time across a couple of packs instead of one. Owners who’ve owned the smaller Worx 20V for years describe being floored by the power jump.
Two things to know before buying: it’s a heftier unit at 11.9 pounds, so a sling or harness helps carry it, and battery life is the most-discussed trade-off — heavy throttle drains a 4.0Ah pack quickly, with slower charging requiring planning for longer sessions.
What stands out: the flexibility to run other Worx attachments plus two batteries on hand.
Size your expectations: heavy power means heavy consumption — bring both packs for bigger jobs.
Pick it if: you want attachment flexibility and a two-battery kit in one purchase.
Otherwise: if portability matters, the heavier build is the sticking point.
10. RYOBI 16″ Carbon Fiber Shaft String Trimmer with 40V HP Brushless Motor
A RYOBI HP brushless head built to muscle through overgrown brush with over 45 minutes of runtime.
This is the trimmer for the homeowner with a jungle to tame. The 40V HP brushless motor delivers more power than a 27cc gas trimmer per the maker, and with a 40V 4Ah battery you get over 45 minutes of cutting. It’s EXPAND-IT capable too, so one power head can drive other attachments when you need them.
In heavy brush, note the real-world drain: reviewers point out a battery dying in about 20 minutes during aggressive cutting, so plan on a second pack if your first job is thick. It’s also a heavier tool — a shoulder strap helps over a long session. Assembly is easy, and once set up, it runs great.
One practical caution: it’s tool-only, so it needs a RYOBI 40V battery to run. A few users have had trouble changing cutter heads, so if you’re not handy with a string head, budget a little time for the first swap.
The upside: serious brush-clearing power and long run time make this a genuine gas replacement for a suburban lot.
Plan around: heavy cutting chews the battery fast, and the tool-only format assumes you already own RYOBI 40V packs.
Great for: RYOBI-platform owners with overgrown patches that need real muscle.
Not ideal if: you’re battery-less or you want a light, nimble trimmer for edges.
11. Greenworks 40V 16 in Cordless String Trimmer, 4.0 Ah Battery
A 16-inch brushless trimmer with a big 4.0Ah battery and the option to add matching yard attachments.
For a larger lot, this Greenworks covers serious ground. The 16-inch cutting swath and brushless motor team up for more power and longer run times, and with the included 4.0Ah battery shoppers say finishing a full yard on a single charge. It’s attachment-capable too — compatible with Greenworks PAC458 (Edger), PAC459 (Hedge), PAC460 (Polesaw), PAC461 (Cultivator), and PAC462 (Blower) add-ons, so the power head grows with your needs.
A two-speed selector plus a variable-speed trigger gives you control near fences and beds, and the maker says it’s 25% lighter than comparable gas models. In practice owners love the top-mounted motor and the durability of the thicker line, using the slower setting near delicate edges.
The drawbacks are weight and string. At 15.2 pounds it’s heavy after a while even with a strap, and one owner reports the line occasionally binding in the spool and breaking after a few minutes. Winding string takes a bit of strength, so budget for that.
The upside: a big battery plus a wide brushless cut and a clear attachment path make this a strong large-yard choice.
Plan around: the heft and occasional string-spool binding — a spare battery and some patience with winding help.
Ideal for: bigger yards where a wide 16-inch cut and a 4.0Ah battery mean fewer interruptions.
Look elsewhere if: a lighter tool is your priority — this is a substantial trimmer to carry.
Understanding the Specs
Cutting Width (Inches)
The width of the circle the spinning line sweeps — 12 inches up to 17 inches here. A 17-inch swath covers more ground per pass than a 13-inch head, so you finish a fence line faster. Narrower widths like 12 inches are easier to steer around flower beds and tight corners.
Battery Capacity (Ah)
Amp-hours measure how much charge a battery stores. A 4.0Ah pack holds more than a 2.0Ah pack, and on most of these tools a bigger cell translates to longer run time before a recharge. All the batteries here are the lithium-ion type.
Motor Type: Brushless vs Brushed
A brushless motor has fewer rubbing parts, so it runs cooler, cuts longer per charge, and lasts longer than a brushed motor. It also holds RPM better in thick grass, which is why it’s common on pricier models.
String Feed and Line Size
Bump feed releases line when you tap the head on flat ground; auto-feed dispenses line as the head spins. Line size like.080-inch suits light trimming, while.095-inch handles heavier weeds — thicker line cuts more but needs more motor power.
FAQ
Will a 40V trimmer replace my gas weed eater?
How long does a 40V trimmer battery last on one charge?
What cutting width should I pick for my yard size?
Do the batteries and chargers come in the box?
Can I use the same battery across different yard tools?
Is a brushless motor worth paying more for?
What size trimmer line should I use?
Are these trimmers attachment capable?
How heavy is a 40V trimmer and do I need a strap?
Can I edge with a string trimmer or do I need a separate tool?
Final Thoughts: The Verdict
For most homeowners, the 40v trimmer winner is the BLACK+DECKER 40V MAX 13 in String Trimmer (LST136) because it nails the everyday job — the fastest 8500 RPM cutting speed here, a tool-free flip to edger, and a complete battery-and-fast-charger kit in the box. If a wide 17-inch swath and thick 0.095-inch line are what you want for heavy weeds, grab the RB 17″ 40V Cordless String Trimmer. And for the buyer who wants one power head to drive a whole set of yard attachments, the SKIL PWR CORE 40 Multi-Head System is the one to reach for. If you already run RYOBI 40V batteries, the bare-tool RYOBI 40V HP Whisper Series 17 in. is a quiet, wide-swath add-on worth grabbing.
How We Picked
We do not accept paid placement. Every pick is matched to a real buyer and a real use-case; we do not hands-on test units.
Sources & Methodology
Specifications: manufacturer listings and product documentation. Review insights: verified customer reviews, as of September 2026. Pricing: not shown on this page (it changes often); check the current price via the retailer link.
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