Line weight
Also called WT, fly line weight, 5-weight
The number from 1 to 12 that grades fly line by mass. The rod and the line have to share it or the outfit will not cast.
Fly casting works by throwing the weight of the line, not the weight of the fly. A fly weighs almost nothing, so the rod has to be loaded by the line itself. The two therefore have to be matched. A 5-weight rod is built to bend properly under the mass of 5-weight line.
Put 8-weight line on a 5-weight rod and it overloads the blank and collapses. Put 3-weight line on it and there is not enough mass to bend the rod at all, so the loop never forms. This is the mistake that makes people conclude fly casting is impossible, and it is the reason matched combos exist.
A 5-weight is the trout all-rounder. Go lighter, 3 or 4, for small streams and delicate presentations. Go heavier, 7 or 8, for bass, pike and anything windy.
If you buy one fly outfit, buy a 9-foot 5-weight. It covers trout, panfish and small bass without arguing.
Common questions
What weight fly rod should a beginner buy?
A 9-foot 5-weight. It handles trout, panfish and small bass, casts in moderate wind, and is the size nearly every beginner combo is built around.
Related terms
Where this comes up
The guides that use line weight and show it on real gear.
Line weight is one of 206 terms in the glossary.
Browse the full fishing glossary