Buy this line
—
weight
Fly line weight is not a pound test — it is a weight in grains, measured over the first 30 feet. Enter your rod and what you are fishing to find the line number to buy, and the grain weight behind it.
| Line | First 30 ft (gr) | (g) | Note |
|---|
Every other kind of fishing line is rated by how much it holds. A fly line is rated by how much it weighs, because the line is the casting weight — there is no lead to throw.
The AFTMA standard (now administered by the American Sportfishing Association) fixes the weight of the first 30 feet of line for each number. That front 30 feet is what is airborne during a cast, so that is what loads the rod. A #5 line carries 140 grains; a #8 carries 210.
| Rod | Line | First 30 ft | Typical use |
|---|---|---|---|
| #3 | #3 | 100 gr / 6.5 g | Small-stream trout, delicate dry flies, tight cover |
| #4 | #4 | 120 gr / 7.8 g | Small to medium trout streams, the classic dry-fly rod |
| #5 | #5 | 140 gr / 9.1 g | The all-round trout rod — dries, nymphs and small streamers |
| #6 | #6 | 160 gr / 10.4 g | Big trout water, bass poppers, medium streamers, light saltwater |
| #7 | #7 | 185 gr / 12.0 g | Bass bugs, carp, small steelhead, windy days |
| #8 | #8 | 210 gr / 13.6 g | Pike, big bass flies, bonefish, most saltwater flats |
| #9–#10 | #9–#10 | 240–280 gr | Salmon, steelhead, big saltwater flies, heavy wind |
| #11–#12 | #11–#12 | 330–380 gr | Trophy saltwater, tarpon, offshore fly fishing |
Few experienced fly anglers fish the line number printed on the rod. Matching the rod to the job matters more than matching it to the label.
| Adjustment | Do it when | What you gain |
|---|---|---|
| Up one size | Wind, heavy flies, fast rod, short casts with big bugs | The rod loads with less line out, flies turn over, distance into wind improves |
| Same size | General nymph and dry fly fishing | The balance the rod was designed for |
| Down one size | Clear, flat water, spooky fish, slow rod already feels heavy | Softer landings and a quieter presentation |
A sinking line of the same number weighs the same in the air but feels heavier because it is denser. Most anglers drop one size on a full-sink or intermediate line for that reason.
The line number is only the first decision. Tippet size follows fly size, and the leader is the part the fish sees.
The all-round trout line. Weight-forward tapers are the default for a reason: they load the rod at normal fishing distance.
Check current price on Amazon →Match tippet to fly size. A 5X tippet handles most #14 to #18 trout flies in clear water.
Check current price on Amazon →For subsurface work and clear water. Fluorocarbon sinks, so it takes a nymph down faster than nylon of the same size.
Check current price on Amazon →TackleCalc is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program that lets sites earn fees by linking to Amazon. Prices and availability are set by Amazon and change without notice. Read our full affiliate disclosure.
Full detail for every calculator is on the methodology page.
Fly line weight is a system, not a single number. The fly leader length calculator builds the leader that turns the line over, the rod power and action guide explains what the rod is rated for, and the leader size chart covers tippet diameters.
If you want the standard weight windows rather than a calculation, the fly line weight chart lists every line weight from 1 to 12 in grains and grams, with what each weight is used for.
It means the rod is designed to load with a number 5 fly line, which carries 140 grains in its first 30 feet. That front 30 feet is the only part the AFTMA standard measures, because it is the only part that is in the air and loading the rod during a cast.
Yes, and many anglers do on purpose. Up-lining one size loads a fast rod more deeply, helps in wind, and turns over heavy streamers. What you lose is delicacy — a heavier line lands harder and can spook fish in clear, flat water.
A grain is an old unit still used for fly lines and arrows: 1 grain equals 0.0648 grams. A 5-weight line weighs 140 grains, or about 9.1 grams, in its first 30 feet. The term survives because fly lines were specified in grains long before metrication.
You are over-lined — the line is too heavy for the blank, so the rod cannot recover between strokes and the loop collapses. If instead the rod will not load at all and the line drops on the forward cast, you are under-lined. Those two symptoms tell you which way to adjust.
A 6-weight covers most bass fishing with poppers and medium streamers. For pike and large bass bugs, go to an 8-weight — you need the mass to turn over a big, wind-resistant fly. Saltwater and big streamers start at 8 and go up to 10 or 12.
Hook Size Selector · Leader size chart · Hook sizes explained · Line Diameter Converter · Braid vs mono vs fluorocarbon
Weight and depth: Lure Weight Calculator · Jig Head Weight Calculator · Sinker Weight Converter · Lure Sink Rate Calculator · Trolling Depth Calculator · Downrigger Depth Calculator
Line and leader: Braid to Mono Converter · Line Diameter Converter · Reel Line Capacity Calculator · Shock Leader Calculator · Fly Leader Length Calculator
Knots and hooks: Knot Strength Calculator · Hook Size Selector
Reel, drag and cast: Reel Gear Ratio Calculator · Casting Distance Calculator · Drag and Leader Calculator
Fish and catch: Fish Weight Calculator · Fillet Yield Calculator
Reference charts: Fly Line Weight Chart
Also worth reading: Fly line weight chart
Please note: every figure on this page is an estimate, not a measured result. Tolerances between brands, wear on your gear and your own setup all change the outcome. TackleCalc has no connection to any brand mentioned here, and this content is for reference only.