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Steel, Aluminum Plate and Bar Weight Calculator

This calculator returns the theoretical weight of plate, flat, round bar, square bar and hex bar in the metals buyers and estimators quote every day. It also gives kg per metre, which is the number most mill price lists and ERP item masters use.

Your numbers

Nominal density. Use the mill certificate value for exact stock.

mm

Plate width, round diameter, square side or hex across-flats size.

mm

Used for plate and flat only. Ignored for bar shapes.

mm
pcs
per kg

Optional. Leave at your quoted price per kg to get a cost estimate.

Your results

Weight per piece (kg)
157
Total weight (kg)
628
Cross-section area (mm2)
10,000
Plate: width x thickness. Round: pi x d squared / 4. Square: side squared. Hex: 0.866 x across-flats squared.
Weight per metre (kg/m)
78.5
Total weight (lb)
1,384.503
Material cost
$754

Theoretical weight from nominal density and nominal dimensions. Mill tolerances, corner radii, rolling margin and kerf are not included.

Save results:

Total weight vs plate thickness

Sweeps Plate thickness from 5 to 50, holding your other inputs fixed.

ERP item weight audit

Optional: we can compare your item master weights with calculated values and flag outliers.

Optional. The tool and every export work without this. No spam.

How to use the calculator

Pick the material, then the shape. For plate or flat enter width and thickness; for bars enter the single size (diameter, side or across-flats) and leave thickness alone. Enter piece length and quantity to get piece weight, total weight in kg and lb, and a cost line if you type your price per kg. The chart sweeps plate thickness from 5 to 50 mm so you can see how fast weight and cost climb when a drawing moves to the next standard gauge.

  • All dimensions are in millimetres, density in g/cm3
  • Thickness is ignored for round, square and hex bar
  • Use the cost field for quick RFQ comparisons, not for final quotes
  • Change quantity to see order weight for freight planning

The formula behind the result

Weight equals volume times density. With dimensions in mm and density in g/cm3, weight in kg is area (mm2) x length (mm) x density / 1,000,000. Areas are width x thickness for plate, pi x d squared / 4 for round, side squared for square, and 0.866 x AF squared for a regular hexagon. A 20 mm round steel bar has an area of 314 mm2, so at 7.85 g/cm3 it weighs about 2.47 kg per metre, which matches published bar tables.

Worked example and how to read it

A 1000 x 10 mm carbon steel plate cut to 2000 mm has an area of 10,000 mm2 and weighs 157 kg per piece; four pieces are 628 kg, about 1,384 lb. Compare that against the mill certificate or the weigh-bridge ticket. Rolled plate is commonly a few percent heavier than theoretical because thickness tolerance is usually positive-biased, so buyers often accept up to roughly 3 to 5 percent variance between theoretical and weighed mass.

Common mistakes and ERP notes

The usual errors are mixing inches and millimetres, using the wrong density for stainless or aluminum, and forgetting that hex size is across flats, not across corners. In an ERP, store the weight per unit of measure on the item master (SAP gross and net weight on the material master, SyteLine item weight, Epicor part weight) so freight, costing and shipping documents agree with what you quote here.

  • Do not use steel density for aluminum or stainless
  • Hex across corners is about 1.155 times across flats
  • Cut loss and offcuts are not in theoretical weight
  • Check your ERP weight unit of measure before loading

Frequently Asked Questions

What is the weight of a steel plate per square metre?

For carbon steel at 7.85 g/cm3, weight is 7.85 kg per square metre per millimetre of thickness. A 10 mm plate is about 78.5 kg per square metre, and a 20 mm plate is about 157 kg per square metre.

How do I calculate round bar weight per metre?

Multiply diameter squared (in mm) by 0.006165 for carbon steel to get kg per metre. This is pi / 4 x 7.85 / 1000. For aluminum 6061 use 0.002121, since the density is 2.70 g/cm3.

Is theoretical weight the same as actual weight?

Not exactly. Mill tolerances on thickness, width and length mean actual weight differs from nominal by a few percent. Contracts usually state whether you pay on theoretical or weighed mass, so confirm before comparing invoices.

Which density should I use for stainless steel?

Use about 7.93 g/cm3 for austenitic 304 and about 8.00 g/cm3 for 316. Ferritic and martensitic grades such as 430 and 410 are closer to 7.70 to 7.75 g/cm3. Check the datasheet for duplex and precipitation grades.

If your item master weights are wrong or missing, Netray can help build a read-only check that compares ERP weights with calculated values. Ask for a short review.

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