Rebar Weight
Calculate the weight of reinforcing steel bars from diameter, length, quantity and steel density. Get weight per bar and total weight in kg and pounds, plus kg/m for site checks.
Estimate Reinforcing Steel Weight
Rebar Weight
Where:
- \(m\) — weight of one bar (kg)
- \(d\) — nominal bar diameter (m)
- \(L\) — length of one bar (m)
- \(\rho\) — density of steel, typically 7850 kg/m³ (490 lb/ft³)
The total weight of the order is simply the weight per bar multiplied by the number of bars: \( M = n \times m \). The formula computes the volume of a cylinder (the bar) and multiplies it by the density of steel.
Rebar Weight – Calculation Example
Example: a delivery of 10 deformed rebar bars, each 16 mm in nominal diameter and 12 m long. Steel density is 7850 kg/m³.
\[ m = \frac{\pi \times 0.016^{2}}{4} \times 12 \times 7850 = 18.94 \text{ kg} \]
\[ M = 10 \times 18.94 = 189.40 \text{ kg} \]
Result: each bar weighs ≈ 18.94 kg (≈ 41.75 lb), and the total weight is ≈ 189.40 kg (≈ 417.55 lb). The linear weight is ≈ 1.578 kg/m, which matches the quick site rule \( d^{2}/162 = 16^{2}/162 \approx 1.58 \) kg/m.
How to use the calculator
- Enter the Bar diameter (d) and pick its unit — mm, cm or in. Use the nominal diameter (e.g. 8, 10, 12, 16, 20, 25, 32 mm).
- Enter the Bar length (L) of a single bar and choose m, cm or ft.
- Enter the Quantity (n) — how many bars of this size you are weighing.
- Check the Steel density (ρ). The default of 7850 kg/m³ (490 lb/ft³) is correct for standard reinforcing steel.
- Read the results: Weight per bar in kg and pounds, plus kg/m, and the Total weight for the whole quantity.
What is rebar weight and why it matters
Rebar (reinforcing bar) is the steel reinforcement embedded in concrete to carry tensile loads. Estimating its weight is a routine task in construction: it determines transport costs, crane lifting plans, ordering quantities and billing. Reinforcing steel is almost always purchased and priced by weight (per kg or per tonne), so converting a bar schedule into kilograms is essential for budgeting and for checking deliveries on site.
The calculation is straightforward: a rebar is a long cylinder, so its volume is the cross-sectional area \( \pi d^{2}/4 \) times its length, and its weight is that volume times the density of steel. Note that deformed (ribbed) bars are specified by their nominal diameter, which is the diameter of an equivalent plain round bar — the ribs do not add weight, so no correction is needed.
For a quick site check when the density is 7850 kg/m³, there is a well-known rule of thumb: the linear weight in kg/m equals the diameter in millimetres squared, divided by 162. For a 16 mm bar this gives \( 256/162 \approx 1.58 \) kg/m, which agrees with the exact value of 1.578 kg/m. The calculator shows this shortcut automatically whenever the density is close to 7850 kg/m³.
Reference table: standard rebar sizes
| Nominal diameter | kg/m | lb/ft |
|---|---|---|
| 8 mm | 0.395 | 0.265 |
| 10 mm | 0.617 | 0.414 |
| 12 mm | 0.888 | 0.597 |
| 16 mm | 1.579 | 1.061 |
| 20 mm | 2.466 | 1.658 |
| 25 mm | 3.853 | 2.590 |
| 32 mm | 6.313 | 4.242 |
| 40 mm | 9.865 | 6.629 |
Values assume a density of 7850 kg/m³. Imperial US bar sizes (#3 to #11) correspond to nominal diameters of 9.5, 12.7, 15.9, 19.1, 22.2, 25.4, 28.7, 32.3 and 35.8 mm respectively, so the same formula applies.
Assumptions and limitations
- The calculator assumes straight bars of constant nominal diameter. Bends, hooks, laps and stirrups add length — include them in the bar length for accurate totals.
- Galvanised or epoxy-coated bars weigh marginally more than bare steel; the coating is usually less than 1% of the weight.
- Steel density varies slightly between mills (roughly 7820–7880 kg/m³). If a mill certificate states a different density, enter it for precise results.
- For scheduling complete reinforced-concrete members, the rebar weight is only part of the design — check the structural capacity separately, for example with the beam section modulus calculator or the uniformly loaded simply supported beam calculator.
Frequently Asked Questions
Can I use this for wire mesh, stirrups or square bars?
Yes, with care. Stirrups and links are the same steel, but sum the developed length of all legs and bends rather than the outside dimension. The cylinder formula also suits plain round bar and smooth dowels. For square or flat sections, replace the circular area πd²/4 with width × thickness; for welded wire mesh, use the quoted mass per square metre from the fabric schedule instead.