Estimating steel tonnage before you place an order

Start from the bill of materials, not the drawing area — list every member by section and length, look up its mass per meter from the IS section tables, and multiply.

Add a wastage allowance, typically 3–5% for cutting losses, before converting the total to tonnage for your purchase order.

Cross-check the estimate against a rough benchmark for your building type — most warehouse structures run 25–40 kg of steel per square meter of built area — to catch a bill-of-materials error before it becomes an expensive one.

Order in mill-length increments where possible rather than exact cut lengths — most sections ship in standard 6m or 12m bars, and ordering to that increment avoids paying for cutting waste that a fabricator would otherwise pass back to you.