What Is the Rebar Weight Calculator?
This tool estimates the weight of steel reinforcement bars (rebar) used in concrete construction. Enter the bar diameter, the length of each bar, and how many bars you have, and it returns the unit weight (kg per metre), the weight of one bar, the total weight in kilograms and tonnes, plus total length. It is useful for ordering steel, estimating material cost, and checking delivery quantities.
How to Use It
1. Enter the bar diameter in millimetres (common sizes: 8, 10, 12, 16, 20, 25, 32 mm). 2. Enter the length of a single bar in metres (standard stock is often 12 m). 3. Enter the number of bars. The calculator instantly shows the weight breakdown.
The Formula Explained
The widely used shortcut for the weight of a round steel bar is \(W = d^{2} / 162\), giving kilograms per metre when the diameter d is in millimetres. This is derived from the density of steel (about 7850 kg/m³) combined with the cross-sectional area \(\pi d^{2}/4\), which simplifies to \(d^{2}/162.2 \approx d^{2}/162\). The full formula is:
$$W = \frac{\text{Diameter (mm)}^{2}}{162} \times \text{Length (m)} \times \text{No. of Bars}$$Multiply the unit weight by the bar length and the number of bars to get the total weight.
Worked Example
For a 16 mm bar that is 12 m long, with 10 bars: unit weight =
$$16^{2} / 162 = 256 / 162 = 1.5802 \text{ kg/m}$$Weight per bar =
$$1.5802 \times 12 = 18.963 \text{ kg}$$Total weight =
$$18.963 \times 10 = 189.63 \text{ kg} \approx 0.19 \text{ tonnes}$$Total length =
$$12 \times 10 = 120 \text{ m}$$FAQ
Why d²/162 and not d²/162.2? 162 is the rounded site-standard divisor; the precise value is 162.28. The small difference is negligible for ordering.
Does it work for any bar size? Yes — the formula applies to any round steel bar diameter you enter.
How do I convert to tonnes? Divide the total kilograms by 1000, which this calculator does for you.
