Chainsaw Bar & Chain Sizing: Length, Pitch, Gauge and Drive Links

A replacement chain has to match your guide bar on three numbers — pitch, gauge and drive-link count. Bar length alone isn't enough: two 16-inch chains can have completely different specs and won't swap.

1. Bar length

The nominal length is the usable cutting length, measured from the front of the saw to the tip of the bar and rounded to the nearest inch. It's what the saw is sold as (10", 14", 16", 18"…). Use it to narrow your search, then confirm the other three numbers.

2. Pitch

Pitch is the spacing of the chain: the distance between any three rivets, divided by two. Common pitches are:

• 1/4 in — small pruning saws and top-handle saws
• 3/8 in low profile (also written 3/8" LP or .375 LP) — most homeowner electric and small gas saws
• .325 in — mid-size gas saws
• 3/8 in (full profile) — larger gas saws

3. Gauge

Gauge is the thickness of the drive links where they sit in the bar groove. Common gauges are .043 in, .050 in, .058 in and .063 in. A chain with the wrong gauge will either bind in the groove or sit loose and wobble.

4. Drive-link count

Drive links are the teeth on the underside of the chain that ride in the bar. Count them (or read the number off the old chain's packaging): for example 56 DL or 64 DL. The count sets the chain's length for your bar.

Where to find these numbers

• On the bar: the tail end of the bar (the part hidden under the side cover) is usually stamped with length, pitch and gauge, and sometimes the drive-link count.
• On the old chain: pitch and gauge are often stamped on the drive links. The packaging lists all three numbers or a chain code (for example Oregon S56 = 3/8" low profile, .050", 56 drive links).
• In the manual: the specifications page lists the original bar and chain.

When to replace the chain

• The saw makes fine dust instead of chips.
• You have to push down to make it cut, or it pulls to one side.
• The chain stretches and needs re-tensioning every few cuts.
• Cutters are chipped, cracked or filed down to the wear mark.

Always wear cut-resistant gloves when handling a chain, and set the tension with the saw switched off and the battery removed or the spark plug disconnected.