How Long Is a Kilogram of Wire?

Solid round wire

Using an assumed steel density of 7.85 g/cm³, theoretical mass in kg per metre is approximately 0.00617 × diameter², with diameter in millimetres. For aluminium at 2.70 g/cm³, use approximately 0.00212 × diameter².

Metres per kilogram = 1 ÷ mass per metre. These rounded coefficients are estimating tools, not guaranteed product weights. Steel grade and aluminium alloy can change density.

Reference table

Bare, solid round wire; no coating or spool. Figures use the rounded coefficients above.

Worked example

For 2,000 m of 0.7 mm steel wire: 0.00617 × 0.7² × 2,000 = approximately 6.05 kg of bare metal.

Flat strip and twisted wire

Do not use the round-wire formula for flat strip, hollow sections or mesh. For a solid rectangular aluminium strip, theoretical grams per metre = thickness in mm × width in mm × 2.70. A 1 × 3 mm strip is approximately 8.1 g per metre before allowances for finishing or changes in length during twisting. A finished twisted profile needs its actual material cross-section and length basis checked.

Allow for the supplied product

Coatings add mass. Diameter tolerance matters because round-wire mass changes with diameter squared: 0.52 mm wire has about 8.2% more cross-sectional area than 0.50 mm wire. Net wire weight excludes the spool or packaging; gross weight includes it. Confirm which figure is quoted.

Reference

Royal Society of Chemistry: aluminium density. The steel density above is an explicit assumption; use the agreed grade density or measured mass for closer estimates.