Fishing Reel Line Capacity Calculator

Estimate how much line a reel spool holds.

Spool diameter

Arbor diameter

Spool width

Line diameter

Line capacity 406.25

Line capacity (yd) 444.28

Formula: length ≈ 0.9·(D² − d²)·W ÷ lineDia²

Step-by-step with your numbers:

1. Values used:

2. Spool diameter = 45

3. Arbor diameter = 20

4. Spool width = 25

5. Line diameter = 0.3

7. Line capacity = 406.25

8. Line capacity = 444.28yd

Did we solve your problem today?

Estimate how much fishing line fits on a spool from its dimensions and the line thickness.

The math behind it

Compare the spool's fillable volume to the line's cross-section, with a ~0.9 packing factor.

45 mm spool, 20 mm arbor, 25 mm wide, 0.30 mm line → about 122 m.

Why a packing factor?

Line never winds perfectly, so usable capacity is a bit below the geometric maximum.