Rebar is calculated as a circle of nominal diameter: the ribs are not counted, that is how GOST 34028-2016 defines it and how GB/T 1499.2-2018 counts it too. The area of the circle is multiplied by the steel density of 7.85 g/cm³, and the result is the mass per metre. For Ø12 it is 0.888 kg/m; for Ø16, 1.58; for Ø25, 3.85. The catalogue tables and the weight calculator on this site use the same function, so the number in the article, in the item line and in your specification matches to the last digit.
Formula
m = 0.006165 · d²
m is the mass of 1 m in kg, d the nominal diameter in mm. The coefficient is π/4 · 7.85 / 1000.
Table for all diameters
| Ø, mm | Mass, kg/m | Metres per tonne | 11.7 m bar, kg | 11.7 m bars per tonne |
|---|---|---|---|---|
| 6 | Mass, kg/m0.222 | Metres per tonne4 505 | 11.7 m bar, kg2.60 | 11.7 m bars per tonne385 |
| 8 | Mass, kg/m0.395 | Metres per tonne2 534 | 11.7 m bar, kg4.62 | 11.7 m bars per tonne216 |
| 10 | Mass, kg/m0.617 | Metres per tonne1 622 | 11.7 m bar, kg7.21 | 11.7 m bars per tonne138 |
| 12 | Mass, kg/m0.888 | Metres per tonne1 126 | 11.7 m bar, kg10.4 | 11.7 m bars per tonne96 |
| 14 | Mass, kg/m1.21 | Metres per tonne827.5 | 11.7 m bar, kg14.1 | 11.7 m bars per tonne70 |
| 16 | Mass, kg/m1.58 | Metres per tonne633.6 | 11.7 m bar, kg18.5 | 11.7 m bars per tonne54 |
| 18 | Mass, kg/m2.00 | Metres per tonne500.6 | 11.7 m bar, kg23.4 | 11.7 m bars per tonne42 |
| 20 | Mass, kg/m2.47 | Metres per tonne405.5 | 11.7 m bar, kg28.9 | 11.7 m bars per tonne34 |
| 22 | Mass, kg/m2.98 | Metres per tonne335.1 | 11.7 m bar, kg34.9 | 11.7 m bars per tonne28 |
| 25 | Mass, kg/m3.85 | Metres per tonne259.5 | 11.7 m bar, kg45.1 | 11.7 m bars per tonne22 |
| 28 | Mass, kg/m4.83 | Metres per tonne206.9 | 11.7 m bar, kg56.6 | 11.7 m bars per tonne17 |
| 32 | Mass, kg/m6.31 | Metres per tonne158.4 | 11.7 m bar, kg73.9 | 11.7 m bars per tonne13 |
| 36 | Mass, kg/m7.99 | Metres per tonne125.2 | 11.7 m bar, kg93.5 | 11.7 m bars per tonne10 |
| 40 | Mass, kg/m9.86 | Metres per tonne101.4 | 11.7 m bar, kg115.4 | 11.7 m bars per tonne8 |
The number of bars per tonne is rounded down to a whole number: a tonne of Ø12 is 96 full bars plus a remainder of 1 126 metres minus 96 × 11.7. When ordering in tonnes the remainder lands in the last bundle; when ordering in pieces it is converted back to tonnes by the same table.
Why 11.7 m
GOST 34028 allows stock lengths from 6 to 12 m; Chinese mills cut 9 and 12 m. The 11.7 m stock length became the industry norm because of transport: the internal length of a 40-foot container is 12.03 m, a 12 m bar fits with no margin, while 11.7 m leaves room for slinging and end boards. An open wagon takes 12 m as well, but a batch that travels by container to a warehouse in Tashkent is cut for the container. The length is written into the specification next to the diameter: the bundle mass depends on it directly.
Theoretical and actual
The table gives the theoretical mass. The actual mass per metre deviates from it within the standard’s tolerance: under GB/T 1499.2-2018 that is ±6 % for Ø6–12, ±5 % for Ø14–20 and ±4 % for Ø22–50; under GOST 34028-2016 the tolerance is set by its own table by diameter. The mill may ship by theoretical or by actual weight, GB/T 1499.2 allows both, and this goes into the contract as a separate line, because with shipment by actual weight a tonne of Ø12 on the minus side of the tolerance gives several bars more, on the plus side fewer. The bureau’s inspector at the mill weighs a bundle and divides by the number of bars: this is how the mass per metre is checked without a laboratory.
How to count a bundle
Chinese mills tie bundles of 2–3 t. A Ø12 bundle of 2 000 kg with an 11.7 m bar is 2 000 / 10.4, that is 192 bars; a Ø25 bundle of the same mass is 44 bars. On the tag the mill writes both the mass and the number of bars, and both figures are checked at inspection and at acceptance. For the project the reverse is more convenient: 3 000 m of Ø16 is 3 000 × 1.58 = 4 740 kg, or 256 bars of 11.7 m, or five tonnes with an allowance for cutting.
Theoretical weight at a steel density of 7.85 g/cm³, calculated by the same function as the catalogue tables and the calculator. The actual weight of the batch is by scale and mill certificate.
