Rebar Weight Calculator
Use this rebar weight calculator to estimate reinforcement bar weight from the bar diameter and total length. It helps with ordering, estimating, transport planning, and checking steel quantities before procurement. The calculator can be used for common reinforcement sizes where you need weight per metre, total kilograms, or tonnes.
Note: kg/m ≈ 0.006165 × d² (industry shortcut for steel at ~7850 kg/m³). If you have changed the density in advanced controls, the live results use your custom density, not the shortcut.
How this calculator works
This calculator works out the weight of reinforcement steel from the cross-sectional area of the bar, the total bar length, and the steel density used in the tool. In practice, this is often simplified into a standard weight-per-metre formula based on the bar diameter. Once the weight per metre is known, the total bar weight is calculated by multiplying it by the total length entered. The calculator defaults to a steel density of 7850 kg/m³, which is the standard figure used for most reinforcement bar estimating. If you open the advanced controls, you can change the density to any value between 7000 and 8200 kg/m³ and the results will update accordingly.
Formulas used
bar area (m²) = π × (diameter / 2000)²
weight per metre (kg/m) = bar area × steel density (kg/m³)
total weight (kg) = weight per metre × total length (m)
kg per metre ≈ 0.006165 × d²
kg per metre ≈ d² / 162
tonnes = kilograms / 1000
total weight with wastage = total weight × (1 + wastage % / 100)
Where d = bar diameter in mm, lengths are in metres, and density is in kg/m³. The shortcut formulas are based on standard steel density. If you use a custom density in the advanced controls, the live calculator results use the exact method, not the shortcut.
Rebar weight chart
| Diameter (mm) | Weight (kg/m) | Weight per 6 m bar (kg) |
|---|---|---|
| 6 mm | 0.222 kg/m | 1.33 kg |
| 8 mm | 0.395 kg/m | 2.37 kg |
| 10 mm | 0.617 kg/m | 3.70 kg |
| 12 mm | 0.888 kg/m | 5.33 kg |
| 16 mm | 1.578 kg/m | 9.47 kg |
| 20 mm | 2.466 kg/m | 14.80 kg |
| 25 mm | 3.853 kg/m | 23.12 kg |
| 32 mm | 6.313 kg/m | 37.88 kg |
| 40 mm | 9.865 kg/m | 59.19 kg |
Chart values are standard reference estimates based on normal steel density (7850 kg/m³). Live calculator results may vary if the tool uses a different density setting.
Worked example
For a 16 mm diameter bar, the weight per metre is calculated from the bar's cross-sectional area multiplied by the steel density. At the standard 7850 kg/m³ density, this gives approximately 1.578 kg/m — which matches the shortcut formula 0.006165 × 16² ≈ 1.578 kg/m. If you need 60 metres of 16 mm bar, multiply 1.578 × 60 to get the total bar weight in kilograms, then divide by 1000 to convert to tonnes. If a wastage allowance is entered, the calculator applies it as a multiplier after the base weight is calculated.
Why rebar weight matters
Knowing rebar weight helps with ordering, transport, lifting, and estimating reinforcement quantities before fabrication or delivery. It also makes it easier to compare bar sizes and understand how quickly total steel weight can increase across a project. This tool is for estimating only and does not replace reinforcement design or structural detailing.
Frequently asked questions
Related tools
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- Weight of Concrete Slab Calculator — estimate slab weight in kg, tonnes and lb
Guides worth reading
- Rebar Weight Per Metre: UK Guide — the d²/162 formula, mesh weights, a worked slab and why you buy more steel than you calculate
Disclaimer: This calculator is for planning and estimating only. Actual steel weight may vary slightly with material specification, density, supplier tolerances, and fabrication details. Confirm final requirements with your supplier or engineer where needed.