How Much Backing Should You Put on a Fly Reel?

Backing is one of those things anglers don’t think too much about. It is, however, an important part of your fishing kit and it helps to know how much it …

Backing is one of those things anglers don’t think too much about.

It is, however, an important part of your fishing kit and it helps to know how much it you need.

To put it simply, backing is a soft and limp braided line that you spool on to your fly reel before attaching the fly line. The fly line backing keeps you connected to the fish

You are going to need between 50 and 300 yards of backing, depending on the kind of fishing you are doing.

The amount of fly line backing depends on two things – the power of the fish you are targeting (the main consideration) and the line capacity of your reel (you ideally want to pack out your reel to about a quarter inch from the edge.

The strength of fly line backing you need is usually about 50% more than the strength of tippet you will typically use.

How Much Backing On a Fly Reel Do I Need?

Here are some recommendations for deciding how much fly line backing you need when fly fishing for various species and the strength.


Use 50 yards of 10lb fly line backing


100 yards of 15lb is as much backing as you need (check one here)

Steelhead, Carp

Use 150 yards of 25lb backing

Bonefish and Permit

250 yards of 30lb backing


250 yards of 30lb backing

Tarpon and Large Ocean Fish

400 yards of 40lb plus backing

What is Fly Line Backing Made Of?

There are two types of fly line backing for fly reels: Dacron backing and Gel Spun Poly Backing.

Dacron backing is made from polyethylene terephthalate (or PET). It’s the same recyclable plastic used in water bottles and polar fleece garments. It makes for a supple, limp backing line.

Gel spun poly backing line is made from ultra high molecular weight polyethylene (UHMWPE), resulting in long molecular chains that give it a higher strength to diameter ratio. UMHWPE is also used in bullet resistant jackets and makes for a backing line that can be thinner than Dacron. This is not always an advantange as if you looking to pack out a reel spool to ensure you have a reasonable arbor and hence retrieve rate you actually want a higher diameter!

When should I use each type of backing?

Use Dacron if:

  • You want to pack out the reel. Dacron is about 40% thicker than Gel Spun Poly Backing for the same breaking strain.
  • You want to save money – Dacron backing is a bit cheaper than Gel Spun Poly Backing

Use Gel Spun Poly Backing

  • If you are fly fishing for powerful fish that have the ability to make long runs. Then you need as much backing as possible. Gel Spun is popular for saltwater fly fishing.

Do you need fly line backing?

Yes, you do. For starters you can’t really attach the thick fly line to the spool of the reel anyway, and fly line backing gives you the ability to keep releasing line as required when a fish pulls off the 30 or so yards of fly line from the fly reel.

Buying Fly Line Backing

Backing comes in spools of various lengths ranging from 50 yards right up to 300 yards. Choose the right amount for your reel as you don’t want to have to join strands from different spools. It is possible to do, but every knot in your fly fishing set up introduces a little more weakness so I’d prefer to use a single spool of fly line backing of the required length than, say, joining two 50 yard spools of backing.

How do you attach the backing to the fly line and fly reel?

To attach the fly line backing to the reel spool you need to use an arbor knot. It is a relatively simple fly fishing knot but it is important to tie it correctly. See our arbor knot tutorial page for illustrated instructions and a how-to video. Use the Nail Knot (tutorial here) to attach the backing to the butt end of the fly line, unless it has a welded loop (then you can use a simple loop to loop connection).

Does the color of my backing matter?

No, the color doesn’t matter at all. Most fly line backing is fluoro green or yellow in color, although some brands are orange. The color is not important, although I guess in some circumstances it is preferable to be able to see the backing line in the water so you can use the rod tip to keep it away from abrasive things in the water such as pylons and snags.

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Rick Wallace is a passionate angler and fly fisher whose work has appeared in fishing publications including FlyLife. He's appeared in fishing movies, founded a successful fishing site and spends every spare moment on the water. He's into kayak fishing, ultralight lure fishing and pretty much any other kind of fishing out there.
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