How to Choose a String Trimmer: Yard Size, Power & Weeds
By The DIYPicks Team · Updated July 2026
A string trimmer (a.k.a. weed eater) finishes what your mower can't reach - edges, fence lines, and around trees. The right one comes down to how big your yard is, how tough your weeds get, and whether you'd rather manage batteries or gas. This guide walks the specs that actually matter so you match the tool to the job.
Start with yard size and weed toughness
Small to medium yards with regular maintenance are the sweet spot for battery trimmers. A 40V-56V unit with a 13-15 in swath handles grass, light weeds, and edging quietly, and one charge usually covers the whole job.
Large lots, tall grass, dense weeds, or light brush push you toward gas. A 21cc-plus engine with a 17 in swath clears more per pass and never pauses to recharge - the difference between finishing in one go and swapping batteries repeatedly.
Choose your power source
Battery trimmers win on convenience: instant start, low noise, no fuel or tune-ups, and shared packs across a brand's tools. The trade-off is finite runtime, so buy a spare battery for anything over a quarter acre.
Gas trimmers win on endurance and raw cutting power, but require 2-stroke fuel mixing, more weight (often 11-13 lb), and periodic maintenance. Corded electric trimmers are a cheap, light middle option if you stay near an outlet.
Understand cutting swath and line
Swath is how wide the trimmer cuts. A 13-15 in swath gives better control near beds and obstacles; a 16-17 in swath covers open ground faster but is harder to finesse in tight spots.
Line diameter matters for durability: .065-.080 in suits light grass, .080-.095 in is the versatile all-rounder, and .095 in or thicker takes on heavy weeds. Match the line the head is rated for.
Line feed: bump, auto, or fixed
Bump-feed heads advance line when you tap the head on the ground - simple and common, but you re-wind the spool by hand. Speed-load heads (like Echo's Speed-Feed or EGO's POWERLOAD) make reloading far faster and less fiddly.
Automatic-feed heads advance line for you but can waste line and stall on thick growth. If you trim a lot, prioritize a head that reloads quickly - it saves real frustration over a season.
Weight, shaft, and attachments
Straight shafts give more reach under bushes and along fences; curved shafts feel nimbler for short users and small yards. Check loaded weight - a couple of pounds matters over an hour of trimming.
Attachment-capable systems (EGO Multi-Head, Ryobi Expand-It) let one power head run an edger, pole saw, or cultivator - a smart way to cover edging without buying a separate machine. Consider this if you want to add an edger later.
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Frequently Asked Questions
- What size string trimmer do I need for a small yard?
- A battery trimmer with a 13-15 in swath and .080-.095 in line is ideal for small yards. It's light, quiet, and one charge easily covers the trimming and edging around a typical suburban lot.
- Can a string trimmer edge my lawn too?
- Yes - turn most trimmers vertical to edge along walks, though it takes practice for straight lines. For crisp, consistent borders, a dedicated wheeled edger or an edger attachment on an attachment-capable trimmer does a cleaner job.
- How much line diameter do I need for weeds?
- For heavy weeds and light brush, use .095 in or thicker line and a trimmer rated for it. Thinner .065-.080 in line is fine for regular grass but snaps quickly on tough, woody growth.