Line Capacity Converter
Enter your reel's rated capacity and switch between line types to see how much actually fits.
Capacity depends on line diameter, not pound test. A 20 lb braid is roughly half the diameter of 20 lb mono, so you fit 3-4 times more of it on your reel.
Backing Calculator
How much cheap backing line should you put on first to fill your spool correctly.
Backing is cheap monofilament that fills the bottom of your spool before your expensive main line. Saves money and prevents your spool getting too empty.
Drag Setting Calculator
Calculate the proper drag setting based on your line's breaking strain.
How to set it
Run line through rod, attach scale, pull at 45 degrees until the target weight, then back off drag until line peels.
These are guidelines. Always test your drag setting before fishing. If using braid with a lighter monofilament leader, base drag on the leader's strength instead.
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Line diameter reference table
Line capacity is determined by diameter, not strength. This table shows typical diameters across monofilament, fluorocarbon, and braided line at different pound tests. Diameters vary by manufacturer, but these are standard industry measurements.
| Line strength |
Monofilament |
Fluorocarbon |
Braided |
| 4 lb Light spinning |
0.008 in |
0.007 in |
0.004 in |
| 6 lb Panfish, trout |
0.009 in |
0.009 in |
0.005 in |
| 8 lb Light bass |
0.010 in |
0.010 in |
0.006 in |
| 10 lb General purpose |
0.012 in |
0.011 in |
0.007 in |
| 15 lb Bass, pike |
0.013 in |
0.013 in |
0.009 in |
| 20 lb Saltwater, catfish |
0.016 in |
0.016 in |
0.010 in |
| 30 lb Heavy saltwater |
0.021 in |
0.020 in |
0.014 in |
| 40 lb Inshore, catfish |
0.025 in |
0.023 in |
0.017 in |
| 50 lb Offshore, large catfish |
0.028 in |
0.026 in |
0.021 in |
| 65 lb Big game |
0.032 in |
0.030 in |
0.026 in |
Diameters based on Berkley Trilene (mono), Berkley Vanish (fluoro), and Spiderwire Stealth (braid). Actual measurements vary by manufacturer. Braided line is roughly 35-45% thinner than mono or fluoro at the same pound test, which is why you fit 3-4 times more of it on your reel.
Drag setting guidelines
| Line type |
Drag setting |
| Monofilament Up to 20 lb test |
20% of breaking strain |
| Monofilament 30-50 lb test |
25% of breaking strain |
| Monofilament 80+ lb test |
30% of breaking strain |
| Braided line Up to 20 lb test |
15% of breaking strain |
| Braided line 30-65 lb test |
20% of breaking strain |
| Braided line Over 65 lb test |
25% of breaking strain |
| Fluorocarbon Any test |
20-25% of breaking strain |
These percentages prevent line breakage during runs. Drag too tight and the rod may break; drag too loose and you lose fish. Always test before fishing, and adjust based on rod power and fish species.
Why braid and mono have different capacities
Line diameter depends on material density, not strength. Braided line is made from multiple thin strands twisted together, creating a denser package than monofilament's single solid strand. This means a 30 lb braid is roughly half the diameter of 30 lb mono. When you spool a reel, diameter determines how many wraps fit, so braid gives you 3-4 times more yardage. Fluorocarbon falls between the two, slightly thinner than mono at the same test.
This is why using a capacity calculator matters. If you assume a reel holds the same yardage regardless of line type, you will either waste expensive line by overfilling or leave your spool dangerously empty and lose casting distance.
Backing: filling your spool correctly
Backing is cheap monofilament or braided line that fills the bottom of your spool before your main line. It serves two purposes: it saves money (why spend ten dollars per spool on premium braided line when you only use the top half?) and it prevents your reel from getting too empty during a long fight, which reduces casting distance.
Typical backing is 20-30 lb monofilament on saltwater reels or 15-20 lb on spinning reels. You do not need to match the strength of your main line; backing is just there to fill space. If your reel is rated for 300 yards of 20 lb mono and you only want 200 yards of your actual fishing line, use 100 yards of 20 lb mono backing underneath it.
Practical example: switching from mono to braid
You have a spinning reel rated for 300 yards of 20 lb monofilament. You want to switch to 30 lb braided line for better sensitivity and durability.
Step 1: Look up the diameters. 20 lb mono is 0.016 in, and 30 lb braid is 0.014 in.
Step 2: Use the formula: 300 x (0.016 / 0.014) squared = 300 x 1.31 = 393 yards.
Step 3: You can fit 393 yards of 30 lb braid on a reel rated for 300 yards of 20 lb mono.
Step 4: Set your drag at 20% of 30 lbs = 6 lbs.