What is fishing line

Fishing line is the only part of the tackle that stays in the water from end to end and takes the whole weight of a fish. It is chosen not by the name on the packet but by three properties: those are exactly what separate the three families of line from one another.

The three properties the choice rests on

Stretch, visibility under water and density — that is the whole set. Braided line barely stretches, shows up in the water and is lighter than it. Monofilament line stretches noticeably, shows moderately and is close to water in density. Fluorocarbon stretches little, is almost invisible in water and sinks.

Everything else — sensitivity at range, how a knot behaves, casting distance, how deep the rig runs — is derived from those three properties. That is why the subsections here are organised by them rather than by brand or price.

How line is labelled

Two numbers appear on the packet: diameter in millimetres and breaking strain. The second is given either in kilograms or in pounds, marked lb. One pound is 0.454 kilograms, so 20 lb is roughly 9 kilograms.

A third number gives the length on the spool: 100, 150, 300 metres, or a bulk spool. Check it against the capacity of your reel spool, which is printed on the spool itself as a diameter-and-metres pair.

All of these describe new line pulled straight and without a knot. Real tackle behaves differently, and that is the point below.

Why the number on braid is not a diameter

Alongside the millimetres, braid often carries a PE number: #0.6, #1.5, #2.0. This is a Japanese sizing system in which the figure denotes a thickness class, not a measured diameter.

Braid is also not round in cross-section — it is woven from several fibres, and a single figure describes such a thread only roughly. Because of this, the same PE number from two makers can mean different real thicknesses. Comparing by breaking strain is more reliable than comparing by number.

Breaking strain and the knot

The stated strength is the strength of an unbroken length. Any knot reduces it: line fails not in the middle but where it was bent and pulled tight. So the margin you leave is not superstition — the knot will certainly take part of the strength away.

The second thing that decides is the tackle. Line has to match the rod rating, and ratings are covered in the fishing rods section.

What we do not write here

We do not name a best line: there is no such thing, because the three properties pull against each other and a gain in one is always a loss in another. We name no brands and compare no prices — those change faster than a reference is updated.