What Is Steel Weight?
Steel weight is the mass of a steel bar based on its diameter, length and the density of steel. In construction, steel weight is commonly calculated in kilograms (kg).
Accurate steel weight calculations are useful for estimating reinforcement quantities, material requirements and approximate project costs.
Steel Weight Formula
A commonly used formula for estimating the weight of a round steel bar is:
Standard Formula
Weight = D² × L ÷ 162
Where D is the bar diameter in millimetres and L is the bar length in metres.
What Do D and L Mean?
| Symbol | Meaning |
|---|---|
| D | Steel bar diameter in millimetres |
| L | Steel bar length in metres |
| 162 | Common constant used for the practical steel weight formula |
Steel Weight Calculation Example
Suppose you have a 12 mm diameter steel bar with a length of 12 metres.
D = 12 mm
L = 12 m
Weight = 12² × 12 ÷ 162
≈ 10.67 kg
Steel Weight Per Metre
The same formula can be used to estimate the weight of one metre of a steel bar.
Weight per metre = D² ÷ 162
For example, a 12 mm bar has an approximate theoretical weight of 0.89 kg per metre.
Common Steel Bar Weights
The following values are approximate theoretical weights per metre based on the standard formula.
| Bar Diameter | Approx. Weight / m |
|---|---|
| 8 mm | 0.40 kg |
| 10 mm | 0.62 kg |
| 12 mm | 0.89 kg |
| 16 mm | 1.58 kg |
| 20 mm | 2.47 kg |
| 25 mm | 3.86 kg |
Calculate Total Steel Weight
If you know the number of bars and the length of each bar, calculate the weight of one bar first and then multiply it by the number of bars.
Total Weight = Weight per Bar × Number of Bars
For example, if one 12 mm bar weighing approximately 10.67 kg is used and there are 20 bars:
10.67 × 20 ≈ 213.4 kg
Important Note About Steel Weight
The formula provides a theoretical estimate based on the diameter and density of steel. Actual supplied steel can vary slightly because of manufacturing tolerances and product specifications.
For project procurement and billing, use the applicable manufacturer, supplier or project specification where required.
Calculate Steel Weight
Enter the bar diameter and length to quickly estimate steel weight.
Steel Weight FAQs
What is the formula for steel weight?
For a round steel bar, a commonly used formula is D² × L ÷ 162, where D is the diameter in millimetres and L is the length in metres.
How much does a 12 mm steel bar weigh per metre?
A 12 mm steel bar has an approximate theoretical weight of 0.89 kg per metre.
How do I calculate the weight of a steel bar?
Enter the bar diameter and length into the standard steel weight formula. The result gives an approximate theoretical weight in kilograms.
Is the D² ÷ 162 formula accurate?
It is a widely used practical formula for estimating the theoretical weight of round steel bars. Actual supplied weight can vary slightly due to manufacturing tolerances.