Coil weight calculator: length, diameter, PIW and slit coils
For metal coil: steel, stainless, aluminium, copper and brass. Enter what you know and it gives you the rest, in metric or imperial, plus the numbers most coil calculators leave out: what one slit strip weighs, how many of them fit across the width, and how long the coil takes to run.
Densities are nominal for the grade, so a weight from geometry is an estimate and not a weighbridge figure. Coating, temper and grade all move it. Length and diameter do not depend on density and are exact for the numbers you typed.
Steel coil weight chart
How much a steel coil weighs depends mostly on its outside diameter, because the diameter is squared. Width only scales the answer. So the useful chart is the weight of each unit of width at each diameter: multiply by your width and you have the coil. Figures are for steel at 7.85 g/cm³, the density the calculator uses for hot rolled, cold rolled, galvanised (GI) and pre-painted (PPGI) coil.
Metric, in kg
| Outside diameter | kg per mm of width, 508 mm bore | kg per mm of width, 610 mm bore | 1,000 mm wide coil, 508 mm bore | 1,250 mm wide coil, 508 mm bore | 1,500 mm wide coil, 508 mm bore |
|---|---|---|---|---|---|
| 1,000 mm | 4.57 | 3.87 | 4,574 kg | 5,718 kg | 6,861 kg |
| 1,200 mm | 7.29 | 6.58 | 7,287 kg | 9,109 kg | 10,931 kg |
| 1,400 mm | 10.49 | 9.79 | 10,493 kg | 13,116 kg | 15,740 kg |
| 1,600 mm | 14.19 | 13.49 | 14,192 kg | 17,740 kg | 21,288 kg |
| 1,800 mm | 18.38 | 17.68 | 18,385 kg | 22,981 kg | 27,577 kg |
| 2,000 mm | 23.07 | 22.37 | 23,070 kg | 28,838 kg | 34,606 kg |
Imperial, in lb
| Outside diameter | PIW, 20 in bore | PIW, 24 in bore | 36 in wide coil, 20 in bore | 48 in wide coil, 20 in bore | 60 in wide coil, 20 in bore |
|---|---|---|---|---|---|
| 36 in | 200 | 160 | 7,185 lb | 9,580 lb | 11,974 lb |
| 42 in | 304 | 265 | 10,937 lb | 14,583 lb | 18,229 lb |
| 48 in | 424 | 385 | 15,267 lb | 20,357 lb | 25,446 lb |
| 54 in | 560 | 521 | 20,175 lb | 26,900 lb | 33,625 lb |
| 60 in | 713 | 674 | 25,659 lb | 34,213 lb | 42,766 lb |
| 66 in | 881 | 842 | 31,722 lb | 42,295 lb | 52,869 lb |
| 72 in | 1,066 | 1,026 | 38,361 lb | 51,148 lb | 63,935 lb |
Reading it. A 1,250 mm coil at 1,600 mm across on a 508 mm bore is 14.19 kg x 1,250 = 17,740 kg. Slit it into 150 mm strips and each one weighs 14.19 x 150 = 2,129 kg, because a slit strip has the same weight per unit of width as the coil it came from.
Other metals. Multiply by the density against steel: x 1.02 for 304 or 316 stainless, x 0.98 for 430 stainless, x 0.34 to 0.35 for aluminium, x 1.14 for copper and x 1.08 for brass. Or pick the metal in the calculator above, which does it for you.
Like the calculator, the chart is an estimate from nominal density, good for planning a crane lift or a load, not for invoicing. Weigh the coil for that.
How many metres of strip are in a coil
Length depends only on the two diameters and the thickness. Width and metal do not come into it, so one chart covers steel, stainless and aluminium alike. On a 508 mm (20 in) bore:
| Thickness | 1,000 mm outside diameter | 1,500 mm outside diameter | 2,000 mm outside diameter |
|---|---|---|---|
| 0.4 mm (0.016 in) | 1,457 m4,779 ft | 3,911 m12,832 ft | 7,347 m24,105 ft |
| 0.5 mm (0.020 in) | 1,165 m3,824 ft | 3,129 m10,266 ft | 5,878 m19,284 ft |
| 0.8 mm (0.031 in) | 728 m2,390 ft | 1,956 m6,416 ft | 3,674 m12,053 ft |
| 1.0 mm (0.039 in) | 583 m1,912 ft | 1,564 m5,133 ft | 2,939 m9,642 ft |
| 1.5 mm (0.059 in) | 388 m1,275 ft | 1,043 m3,422 ft | 1,959 m6,428 ft |
| 2.0 mm (0.079 in) | 291 m956 ft | 782 m2,566 ft | 1,469 m4,821 ft |
| 3.0 mm (0.118 in) | 194 m637 ft | 521 m1,711 ft | 980 m3,214 ft |
| 5.0 mm (0.197 in) | 117 m382 ft | 313 m1,027 ft | 588 m1,928 ft |
If you have the weight off the coil tag rather than the diameter, length in metres = 1000 x weight in kg / (width in mm x thickness in mm x density in g/cm³). A 5,000 kg steel coil 1,250 mm wide at 1.00 mm holds 510 m. In imperial, for steel: feet = pounds / (width in x thickness in x 3.403). The calculator's "I know the weight" mode does this and gives you the outside diameter too.
There is only one idea here
A coil is a long flat strip that has been rolled up, and rolling it up does not change how much metal is in it. So the ring of metal you see looking at the end of the coil has exactly the same area as the strip would have if you unrolled it and looked at it edge on.
That gives two ways of writing the same area, and everything else is those two lines rearranged:
Which is why length does not depend on width, and why width does not appear in the length formula at all. It also explains something that catches people out: doubling the outside diameter roughly quadruples the weight, because the diameter is squared.
The formulas
| You want | Formula | Units |
|---|---|---|
| Weight | A x width x density | mm, g/cm³, divide by 1e6 for kg |
| Length | A / thickness | mm, divide by 1000 for m |
| OD from length | sqrt(ID² + 4 x L x t / pi) | L and t in mm |
| OD from weight | sqrt(ID² + 4 x A / pi) | A from weight and density |
| PIW | weight / width | lb and inches |
| Slit strip weight | parent weight x slit width / parent width | same gauge throughout |
Density is the only input that is not a measurement of your coil. It is nominal for the grade, so a weight computed from geometry is an estimate: coating, temper and grade all move it, and a galvanised coil weighs more than the base steel it started as. Length and diameter do not involve density at all and are exact for the numbers you type.
A worked example
Cold rolled steel, 1500 mm outside diameter on a 508 mm mandrel (a 20 inch mandrel), 1250 mm wide, 1.00 mm gauge, density 7.85 g/cm³.
- Area. (pi / 4) x (1500² minus 508²) = 1,564,463 mm²
- Weight. 1,564,463 x 1250 x 7.85 / 1e6 = 15,351 kg
- Length. 1,564,463 / 1.00 / 1000 = 1,564 m
- Check it. Length x thickness x width x density has to give the weight back: 1564.46 x 1000 x 1.00 x 1250 x 7.85 / 1e6 = 15,351 kg. It does, so the two formulas agree.
- PIW. 15,351 kg is 33,844 lb, and 1250 mm is 49.21 in, so 688 lb per inch of width.
- One 152 mm strip. 15,351 x 152 / 1250 = 1,867 kg, and eight of them fit across 1250 mm with 34 mm left for edge trim.
Slit coil weight, and why PIW makes it easy
Slitting changes width and leaves gauge and length alone, so a slit strip is the parent coil scaled by width. That is the whole calculation, and it is why the trade quotes PIW: once you have pounds per inch of width, a strip's weight is just PIW times its width, whatever the coil it came from.
A useful consequence: a slit strip has the SAME PIW as the coil it was cut from. If you work out a strip's PIW and it differs from the parent, one of your numbers is wrong.
The width that is not sold is edge trim plus whatever is left over from the pattern. That leftover is a planning decision rather than an arithmetic one, and it is what the slitting calculator is for: it works out the knife positions and spacer widths that turn this coil into that set of strips.
Run time: how long a coil takes to slit
Run time is the strip length divided by the line speed, and nothing else. The example coil holds 1,564 m of strip, so at 120 m/min it runs in 13 minutes, and at 60 m/min in 26. The calculator uses whatever line speed you enter, in metres or feet per minute.
That is time with the line at speed. It leaves out threading the coil, ramping up and down, stops, and the changeover before the coil, which on a short run can take longer than the run itself. If you are planning a shift, the changeover is where the minutes go, and the changeover guide breaks it down.
Coil calculation questions
How much does a steel coil weigh?
It depends on the outside diameter far more than on the width, because the diameter is squared. On a 508 mm (20 in) bore, each millimetre of width weighs 7.29 kg at 1,200 mm across and 18.38 kg at 1,800 mm, so a 1,250 mm wide coil weighs 9,109 kg at the smaller size and 22,981 kg at the larger. In imperial, a 48 in wide coil on a 20 in bore weighs 20,357 lb at 48 in across and 51,148 lb at 72 in. The chart on this page gives the sizes in between, and the calculator gives any size exactly.
How do you calculate the weight of a steel coil?
Work out the area of the ring of metal you see at the end of the coil, then multiply it by the coil width and by the density of the metal. In millimetres that is weight in kg = (pi / 4) x (OD² minus ID²) x width x density / 1,000,000, with density in g/cm³: 7.85 for carbon and galvanised steel. The coil in the worked example, 1500 mm across on a 508 mm bore and 1250 mm wide, weighs 15,351 kg.
What is PIW and how do you calculate it?
PIW is pounds per inch of width: the coil weight in pounds divided by its width in inches. The trade quotes it because a slit strip weighs PIW times its own width, whatever coil it came from. The example coil is 33,844 lb over 49.21 in, which is 688 PIW.
How do you work out the length of strip in a coil?
Divide the end area of the coil by the strip thickness: length = (pi / 4) x (OD² minus ID²) / thickness. Width and density do not come into it, so the length is exact for the dimensions you enter. The example coil at 1.00 mm holds 1,564 m of strip, about 5,133 ft.
How do you work out coil length from its weight?
Divide the weight by the weight of one metre of strip. In metric, length in metres = 1000 x weight in kg / (width in mm x thickness in mm x density in g/cm³). A 5,000 kg steel coil 1,250 mm wide at 1.00 mm holds 510 m. For steel in imperial, feet = pounds / (width in inches x thickness in inches x 3.403), so a 10,000 lb coil 48 in wide at 0.040 in holds 1,530 ft. This is the calculator's "I know the weight" mode, which gives you the outside diameter as well.
How much does one slit coil weigh?
The parent coil weight times the slit width, divided by the parent width. Slitting changes width and leaves gauge and length alone, so every strip has the same PIW as the coil it was cut from. A 152 mm strip from the example coil weighs 1,867 kg.
What density should I use for steel, stainless, aluminium and copper?
The calculator uses 7.85 g/cm³ for cold rolled, hot rolled, galvanised (GI) and pre-painted (PPGI) steel, 7.80 for galvalume, 7.65 for CRGO and CRNGO electrical steel, 8.00 for 304 and 316 stainless, 7.70 for 430 stainless, 2.70 to 2.71 for aluminium, 8.94 for copper and 8.50 for brass. Those are nominal for the grade, so a weight worked out from them is an estimate. For anything commercial, weigh the coil.
What bore sizes do steel coils come on?
Cold rolled, galvanised and pre-painted coil is usually wound on a 508 mm (20 in) or 610 mm (24 in) bore. Hot rolled coil comes on 508 mm or on about 760 mm (30 in). A slit coil takes the bore of the recoiler mandrel it was wound on. The bigger the bore, the less metal at the same outside diameter: at 1,500 mm across, a 610 mm bore holds 5.7% less than a 508 mm one, which is why the chart gives both.
How long does a coil take to run through a slitting line?
Strip length divided by line speed. The example coil, 1,564 m long, runs in 13 minutes at 120 m/min and in 26 minutes at 60 m/min. That is time with the line at speed; threading, ramping up and down, and the changeover before the coil all come on top.
What this will not tell you
- Whether the coil clears your uncoiler or the crane. Compare the outside diameter against your own limits.
- Whether your tooling can actually build that slit pattern. That depends on the spacers you hold, and it is the question OptiStack Pro answers against your real inventory.
- An exact weight. Nominal density is not your coil's density. For anything commercial, weigh it.
Next
You have the coil. Now work out the knife and spacer stack that cuts it, then check the clearance for the grade on the slitting machine guide.
Open the slitting calculator