| Diameter (mm) | Area (mm²) | Weight (kg/m) | Weight per 12m Bar (kg) |
|---|---|---|---|
| 6mm | 28.3 | 0.222 | 2.66 |
| 8mm | 50.3 | 0.395 | 4.74 |
| 10mm | 78.5 | 0.617 | 7.40 |
| 12mm | 113.1 | 0.889 | 10.67 |
| 16mm | 201.1 | 1.580 | 18.96 |
| 20mm | 314.2 | 2.469 | 29.63 |
| 25mm | 490.9 | 3.854 | 46.25 |
| 28mm | 615.8 | 4.834 | 58.01 |
| 32mm | 804.2 | 6.313 | 75.76 |
| 36mm | 1017.9 | 7.990 | 95.88 |
| 40mm | 1256.6 | 9.864 | 118.37 |
Rebar estimation starts with the structural drawings — specifically the Bar Bending Schedule (BBS). The BBS lists every bar by diameter, shape, cutting length, and quantity. The total running length for each diameter is then multiplied by the unit weight (d²/162.2 kg/m) to get the total weight.
For quick procurement estimates, this calculator lets you enter the total length needed for a given diameter and instantly returns the total weight and number of standard bars required. A typical wastage allowance of 3–5% should be added for cutting and lapping losses.
The most commonly used rebar sizes in construction are 8mm & 10mm for stirrups and ties, 12mm & 16mm for slab reinforcement, and 20mm, 25mm & 32mm for beams, columns and footings.
For 500 metres of 12mm TMT bar with standard 12m bar length: 500 ÷ 12 = 42 bars (rounded up). Total weight: 500 × 0.889 = 444.5 kg (0.445 tonnes).
To calculate rebar for a slab: 1) Determine the slab dimensions and bar spacing. 2) Calculate total running length = (slab length / spacing + 1) × slab width, for both directions. 3) Multiply total length by weight per metre (d²/162.2) to get the total weight.
The standard length of a TMT bar is 12 metres in most markets. Some mills also produce 6m and 9m lengths. Custom cutting lengths may be available on request for large orders.