Cordless Trimmer Line: Matching Gauge to Voltage

On a gas trimmer you mostly choose line gauge by the job. On a cordless trimmer there’s a second constraint: the battery voltage is a good proxy for how much line the motor can actually swing. Match gauge to voltage and the trimmer cuts well and runs long; mismatch it and you’ll either snap line constantly or kill your runtime. Here’s the mapping.

18V–20V — stick to thin line

These small motors don’t have the torque to spin heavy line. Run 0.065” (0.080” at the most). Over-gauging a 20V trimmer drags the motor, tanks the runtime, and often won’t feed at all.

24V–40V — the 0.080” zone

The sweet spot is 0.080”, stepping up to 0.095” for tougher jobs if the head supports it. Most homeowner work lives here — enough power for thicker grass and light weeds without bogging.

56V–80V and gas — heavy line

These have the torque for 0.095” and up, which is what you want for weeds and light brush. Under-gauging a high-voltage trimmer just wastes its capability — the line snaps and you’re refilling constantly.

Voltage-to-gauge cheat sheet

Mismatch symptoms

• Too heavy for the voltage: motor bogs and overheats, line won’t feed, runtime collapses.
• Too light for the voltage: line snaps constantly and cuts poorly in anything but soft grass.

The order of priority

Match the gauge to your head’s rating first (that’s the hard limit — see Choosing Trimmer Line Gauge), then to your voltage, then to the job. Find spools and line for your exact model on the Brands page or in the shop.