How to Calculate Coil Weight: Formula, Worked Examples & Free Calculator

Coil Processing · Published 2026-07-16 · 6 min read · By Friend Engineering Works

A truck arrives with a coil the paperwork says is 18 tonnes. Your crane is rated for 20. Your decoiler for 20. If that number on the paperwork is wrong - or you never checked it - you find out the hard way.

Coil weight is one of those numbers everyone in a steel plant uses daily and almost nobody calculates from scratch. Here's the formula, worked examples for the common materials, and a free calculator that does it in seconds.

The Coil Weight Formula

A coil is a hollow cylinder. Its weight is that cylinder's volume multiplied by the material's density:

Weight (kg) = π/4 × (OD² − ID²) × Width × Density × 10⁻⁶

where:

• OD = outer diameter in mm
• ID = inner diameter in mm (usually 508mm or 610mm in India)
• Width = coil width in mm
• Density = material density in g/cm³

Density Values for Common Coil Materials

Worked Example 1: CR Steel Coil

A cold-rolled steel coil with OD 1500mm, ID 508mm, width 1250mm:

Weight = π/4 × (1500² − 508²) × 1250 × 7.85 × 10⁻⁶ = 0.7854 × (2,250,000 − 258,064) × 1250 × 7.85 × 10⁻⁶ = ≈ 15,350 kg ≈ 15.35 tonnes

You can verify this in the steel coil weight calculator - same numbers, computed instantly.

Worked Example 2: Stainless Steel Coil

An SS 304 coil with OD 1400mm, ID 508mm, width 1250mm:

Weight = π/4 × (1400² − 508²) × 1250 × 7.93 × 10⁻⁶ = ≈ 13.2 tonnes

Note the density: SS 304 uses 7.93, not steel's 7.85 - and SS 430 is lighter still at 7.70. At stainless prices, that 3% difference between grades is real money. The stainless steel calculator has both grades built in.

Worked Example 3: Aluminium Coil

The same 1500/508/1250mm coil dimensions in aluminium (density 2.70):

Weight = ≈ 5.3 tonnes - about one-third of the steel version.

This is why aluminium lines are specified so differently: the aluminium calculator shows the same geometry at a fraction of the load.

Bonus: Strip Length from Coil Weight

If you know the thickness, you can also get the total strip length in the coil:

Length (m) = Weight (kg) ÷ (Thickness × Width × Density × 10⁻³)

The 15.35-tonne CR coil above, at 2mm thickness, contains about 782 metres of strip - useful for estimating run time at a given line speed.

Why Coil Weight Matters

• Decoiler and recoiler sizing - equipment must be rated above your heaviest coil, with at least ~20% margin for dynamic loads. See our decoiler machines rated up to 40 tonnes.
• Crane and coil car capacity - the same margin logic applies to everything that lifts or moves the coil; our coil car buying guide covers sizing in detail.
• Freight and logistics - road transport limits and axle loads are planned from coil weights.
• Commercial verification - a quick calculation catches paperwork errors before they become disputes. For high-value materials like copper, always confirm with a weighbridge; use calculation for planning.

Skip the Manual Math

All of the above is built into our free coil weight calculator - eight materials, kg/tonnes output, strip length, and no sign-up. There are material-specific versions for steel, stainless steel, aluminium, GI, copper and brass.

Sized your coil and need equipment rated for it? Send us the specs - the calculator can carry them straight into the quote form.

← All articles