Construction material calculator
Quantities for blockwork, plaster, reinforcing steel, floor tiles, paint and roofing sheets from your own dimensions. Every assumption is shown and can be changed. For concrete, use the concrete calculator.
Result
- Mass per metre
- 0.888 kg/m
- Total length, with waste
- 126 m
- Mass
- 111.9 kg
- Stock bars of 12 m to buy
- 11
Cutting plan: 2 cut bars from each stock bar, the offcut left over.
Steel is sold by weight or by the bar; confirm which with the supplier, and the grade the drawings specify.
No cost is estimated: the site has no verified material price observations yet, and it does not estimate a cost from an unverified figure.
What this is for
The weight of reinforcing bar for a bar schedule, and how many stock bars to buy. It is an estimate for ordering and checking, not a design or a bill of quantities for a contract.
How it works
- Mass per metre = steel density × π/4 × diameter² (with 7,850 kg/m³ this is diameter² ÷ 162, in mm and kg).
- Total length = number of bars × cut length × (1 + waste %); mass = total length × mass per metre.
- Stock bars: as many cut bars as fit in one stock bar are cut from it; the rest is offcut.
Assumptions
Each one is an input above. None of them is a legal or standard requirement.
| Assumption | Value used | Where it comes from |
|---|---|---|
| Bar diameter | 12 mm | Your choice. |
| Waste allowance | 5 % | Site rule of thumb. Offcuts and laps not already in the cut length. Laps belong in the cut length when you know them. |
| Stock bar length | 12 m | Product size. Bars are commonly supplied in 12 m lengths; use your supplier's length. |
| Steel density | 7850 kg/m³ | Material property. The density used for the nominal mass of reinforcing bars: a 12 mm bar then weighs about 0.888 kg per metre. |
Worked example
Twenty 12 mm bars cut at 6 m are 120 m, or 126 m with 5% waste. A 12 mm bar weighs 0.888 kg a metre, so 111.9 kg. Two 6 m bars come out of each 12 m stock bar: 11 stock bars.
Limitations
- Laps, bends and hooks belong in the cut length; take them from the bar bending schedule.
- The grade and the diameters come from the drawings, not from this tool.
- Quantities only: no labour, transport or cost.
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