Engineering tool
Plate order thickness calculator
Enter the thickness your drawing needs, the plate size and the quantity. The calculator gives the nominal thickness to order under IACS UR W13, the thinnest and thickest a plate may legally be, and the weight at each limit.
Plates
Order thickness
12.5 mm nominal
- Smallest nominal that works
- 12.3 mm
- Thinnest allowed at any point
- 12.2 mm
- Average must be at least
- 12.5 mm
- Weight per piece
- 1.177 t
- Extra weight versus the drawing value
- 0.471 t
Order thickness
20.5 mm nominal
- Smallest nominal that works
- 20.3 mm
- Thinnest allowed at any point
- 20.2 mm
- Average must be at least
- 20.5 mm
- Weight per piece
- 4.828 t
- Extra weight versus the drawing value
- 0.471 t
All plates
- Total weight at nominal
- 31.086 t
- Total weight if all at the lower limit
- 30.521 t
How this was worked out
UR W13.3.2: the minus tolerance is 0.3 mm for hull steel whatever the thickness. Nominal = required + 0.3 mm, rounded up to the ordering step.
UR W13.4.2: the average of the measurements must not be below the nominal thickness.
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What this calculator covers
IACS UR W13 (Rev.6, 2018) for plates and wide flats of 600 mm width and above: the 0.3 mm minus tolerance on hull structural steel (UR W11) and high strength steel for welded structures (UR W16), Table 1 minus tolerances for machinery structure steel, and the rule that the average thickness must not be below the nominal thickness.
What it does not cover
Plus tolerances: UR W13 leaves them to a recognised standard or your contract, so you enter the value yourself. It also does not cover plates ordered to Class C of ISO 7452 (which replaces W13.3), width, length and flatness tolerances, or the mill's own rolling limits. Check the rolled thicknesses and steps with the mill.
Questions engineers ask
- Why does the order thickness come out 0.3 mm above my drawing?
- UR W13 allows a hull steel plate to be 0.3 mm thinner than its nominal thickness at any measured point. A plate ordered at exactly the drawing thickness can therefore be 0.3 mm under it. If your drawing thickness is a minimum at every point, the nominal has to be higher. If your class rules or drawing already include the tolerance, choose the nominal option instead.
- Does the average thickness rule give me extra steel?
- UR W13 requires the average of the measurements not to be below the nominal thickness. A correctly rolled plate is therefore, on average, at or above nominal, and individual points may sit between the lower limit and the upper limit. Whether the contract is priced on nominal or on actual weight changes your cost, so settle that with the mill.
- Why is there no built-in plus tolerance?
- UR W13 says plus tolerances follow a recognised national or international standard or the purchaser's requirement, and it gives no numbers. Those standards have several classes and are not freely published, so the calculator takes the plus tolerance from you rather than guess one. Leave it empty to see only the lower limit.
Source
Minus tolerance, average thickness and the machinery steel table were taken from IACS Unified Requirement W13 (Rev.6, 2018) and checked against the published text. Original: IACS UR W13 (PDF)
This is an arithmetic aid, not an approval. The thickness on your class-approved drawing and the contract with the mill govern. For plates ready to ship, contact us. Request a quote