Calculate the approximate length of metal strip wound into a coil from outside diameter, inside diameter and material thickness. Add strip width and density to estimate coil area and weight.
How do I calculate the length of a metal coil? Enter the outside diameter, inside diameter and strip thickness. The calculator uses the annular-area approximation to estimate the wound strip length.
What is the coil length formula? L ≈ π × (OD² − ID²) ÷ (4t), where L is length, OD is outside diameter, ID is inside diameter and t is strip thickness.
Does coil width affect length? No. Width cancels out of the basic length calculation for a uniform tightly wound strip. Width is needed for weight and area calculations.
Can I calculate steel coil weight? Yes. Enter strip width and choose the appropriate steel density to estimate the coil's material mass.
Can this calculate aluminum coil length? Yes. Coil length depends on geometry and thickness, not material type. Material selection becomes important when estimating weight.
What if the coil is loosely wound? The theoretical formula assumes the strip occupies the wound annular volume efficiently. Gaps or loose winding can make the actual length differ from the estimate.
Why can calculated length differ from supplier records? Possible causes include thickness tolerance, winding tension, measurement error, telescoping, coil shape, gaps and variations in the actual strip dimensions.
Can I use inches? Yes. OD, ID and thickness can be entered in compatible imperial or metric units, and the calculator converts them internally.