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Packaging tool
Solve spool footage or outside diameter from basic winding geometry
Use core diameter, outside diameter, material thickness, and footage to estimate rolled length or final spool size with transparent math.
Spool workspace
All diameters and thickness values are entered in inches. Length is returned in feet and inches using the standard wound-roll area formula.
Inputs can mix inches and millimeters. The solver converts each value internally, then uses L = (pi / (48t)) * (D^2 - C^2) where L is feet and C, D, and t are inches.
Solved results
Final wound OD in inches.
Half the OD-to-core difference.
Radial build divided by thickness.
Notes
Use this space for project notes before saving as PDF.
Disclaimer: Use calculations at your own risk. For critical applications, verify results against your governing standards/specifications.
How it works
- Enter the core diameter and material thickness in inches.
- Choose whether you know the final outside diameter or the total material length in feet.
- The calculator solves the missing value from the wound cross-sectional area relationship.
- Derived values show radial build and an approximate number of wraps for quick shop estimates.
FAQ
What thickness unit should I enter?
Enter thickness in inches. If your material is specified in mils, divide by 1000 first.
Why is wrap count approximate?
The wrap estimate assumes uniform thickness and ideal winding with no air gaps, tension changes, or compression.
Can outside diameter be smaller than the core?
No. The outside diameter must be equal to or greater than the core diameter for a valid spool.