Spool Calculator & Interactive Charts

Use this page to explore spool outer diameters vs. remaining material length and calculate spool capacity.

Chart #1: Outer Diameter vs. Remaining Length (4-inch Core)

Enter values in inches (for thickness and diameters), then click Calculate to find the remaining material in feet.

Material Thickness (inches):

Spool Outer Diameter (inches):

Core Diameter (inches):

We treat the spool of material as a series of wraps, each adding one thickness of the material. The Archimedean spiral approach leads to the formula:

L (feet) = ( π / (48 * t) ) × ( D² - C² )

This formula assumes uniform winding and negligible gaps.