A bar schedule turned into tonnage, with laps and binding wire priced.
Foundation, roof and structure. 5 questions answered below, each with the arithmetic behind it and the limits of what the tool decides. Open the Reinforcement and Bar Weight tool.
Reinforcement is measured in weight, and weight comes from three facts about each bar: its diameter, how many there are and how long each one is. A bar schedule already contains those, which is why the tool asks for the schedule rather than for a percentage of concrete volume. That distinction matters commercially. A rate per cubic metre of concrete for reinforcement is a guess that hides the design, and it is wrong in both directions on different jobs. Counting actual bars tells you what to buy, what to cut and what to bend, and the total in kilogrammes is the figure a fabricator quotes from. Where a bar is entered without a length, the tool reports it rather than assuming an overlap.
Twenty five bars of sixteen millimetre at seven metres weigh sixteen millimetre bar at about one point five eight kilogrammes per metre, so eleven kilogrammes each, and two hundred and seventy six in total. Thirty bars of twelve millimetre at five metres come to about four point four four kilogrammes each, so a hundred and thirty three. Together the schedule is just over four hundred kilogrammes, and with a five percent lap allowance about four hundred and twenty. Nothing in that total came from the concrete volume, which is why it can be checked bar by bar.
A bar schedule. For each bar mark the tool needs a diameter, a length and a number of bars, which is exactly what a bending schedule already states. From those three it calculates the weight using the unit mass of that bar size, sums the marks by diameter, and returns a total in kilogrammes. If you have a drawing without a schedule, the schedule has to be made first, because the weight cannot be inferred from the concrete.
Diameter gives the unit mass, and the mass multiplied by the length gives the weight of one bar, and that multiplied by the count gives the bar mark's total. A sixteen millimetre bar is about one point five eight kilogrammes for every metre, so a seven metre bar is eleven kilogrammes. The unit masses are physical properties of the bar, not market prices, so the arithmetic is the same wherever the steel is being bought.
The common diameters from six millimetres to thirty two, which covers most building work. Ranges beyond that depend on the supplier, and where a bar size is not in the list it can still be entered by its unit mass. Grade matters for strength but not for weight, so a schedule in a higher grade weighs the same as one in a lower grade, which is why the tool asks for diameter rather than grade.
Binding wire is not included, and neither are spacers, chairs or tying labour. They are real costs and they are usually priced per tonne of reinforcement or as a separate sundries line. The estimate covers the bar weight from the schedule, which is what the fabricator quotes and what arrives on the lorry. Adding a wire percentage would be inventing a figure whose basis nobody could check later.
No. It measures the bars you specify. How much steel an element needs, where laps fall, how bars are anchored and curtailed are design decisions that come from the structural engineer's calculations. The tool's value is that it turns a finished schedule into a weight, a cost and an order, and it is deliberately incapable of deciding the schedule itself.