Metal Coil Weight and Length

Finding strip length from a coil

The winding volume is the annular area between its outer and inner diameters multiplied by strip width. The packing fraction specifies how much of this volume is metal. Dividing net metal volume by width and thickness gives the unwound strip length. Multiplying volume by density gives net metal weight.

Starting with net weight

Subtract the core and packaging from the measured gross weight. For example, 800 kg of metal at an example density of 8000 kg/m³ occupies 0.1 m³. A strip 1 m wide and 2 mm thick then has a length of 50 m.

Limits

The density default is a numerical example, not a material specification. Enter the correct value for your alloy and temperature. The default packing fraction assumes an ideal winding. Results do not replace a weighing certificate or a precision length measurement.

The role of width in the diameter calculation

Measure outer diameter across the metal winding and inner diameter at the core surface where winding starts. The core's internal hole is not the winding's inner diameter. Use actual metal thickness. Counting coatings, protective film or gaps as solid metal can overestimate the result. Establish a measurement basis instead of choosing an unsupported packing correction.

For a numerical check, choose outer diameter 600 mm, inner diameter 200 mm, width 500 mm and thickness 1 mm. For ideal, fully packed winding, the annular area is π × (0.6² − 0.2²)/4. Multiplying by width gives metal volume 0.04π m³. Strip cross section is 0.5 × 0.001 m², so length is 80π m, approximately 251.327 m. With a user selected example density of 7000 kg/m³, mass is 280π kg, approximately 879.646 kg. This density is not taken from an alloy table.

At unchanged diameters and thickness, changing width scales both volume and strip cross section equally. Calculated length therefore stays unchanged while mass changes. Use this property to check whether length and weight have been confused.

Frequently asked questions

How do you calculate coil length from coil weight?

For example net metal mass 800 kg, density 8000 kg/m³, width 1000 mm and thickness 2 mm, the resulting strip length is 50 m. Mass is divided by density and cross sectional area, excluding core and packaging mass, and the entered density is an example rather than a material standard.

Calculate with these values