Rebar weight calculator
The weight of a steel bar per metre in kg is its diameter in millimetres squared divided by 162.2. Multiply by the total length of bars and add a lap and wastage allowance to get kg, then divide by 1,000 for tonnes. Enter a price per tonne to see the cost.
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The formula and the constant
Weight per metre (kg/m) = d x d / 162.2, where d is the nominal bar diameter in millimetres. The constant 162.2 comes from the cross-section of a round bar and a steel density of about 7,850 kg/m3. The rule of thumb d squared over 162 is also common and gives a slightly higher weight, and the equivalent 0.00617 x d squared appears in some references, so tables from different sources can differ in the third decimal place.
This calculator and the table below use 162.2 throughout, so the table matches the result the calculator gives. It offers the diameters 6, 8, 10, 12, 16, 20, 25, 32 and 40 mm. Preferred sizes differ between countries, and your drawings decide which you use.
From bars to tonnes
Total length = number of bars x length of each bar. Weight = weight per metre x total length x (1 + lap and wastage %). The tool shows the weight in kg and in tonnes and, if you enter a price per tonne, the cost before VAT. The lap and wastage percentage is yours to set from your bar bending schedule, cutting plan and the lap lengths on the drawings.
This is a weight estimate. It does not check bar grade, lap lengths or any code requirement, and it is not a substitute for a bar bending schedule. Steel is checked on delivery through a material inspection report.
Ordering and receiving steel
Steel is bought and delivered by weight, so a calculated figure helps you compare quotes and check the delivery note. In SupaJack Construct site stores records what arrived and what was installed, wasted or missing, and quality and handover keeps inspection reports with their attachments. Read the procurement guide, the document control guide and the glossary entries for a goods received note and a submittal.
For cost and claims use the VAT calculator, the payment certificate calculator and the retention calculator. Related tools are the ready-mix concrete calculator and the earthwork volume calculator.
Weight per metre table
Values are d x d / 162.2, rounded to 3 decimals. The last column is the weight of a 12 m length.
| Diameter | Working | kg per metre | kg per 12 m bar |
|---|---|---|---|
| 6 mm | 6 x 6 / 162.2 | 0.222 | 2.66 |
| 8 mm | 8 x 8 / 162.2 | 0.395 | 4.73 |
| 10 mm | 10 x 10 / 162.2 | 0.617 | 7.40 |
| 12 mm | 12 x 12 / 162.2 | 0.888 | 10.65 |
| 16 mm | 16 x 16 / 162.2 | 1.578 | 18.94 |
| 20 mm | 20 x 20 / 162.2 | 2.466 | 29.59 |
| 25 mm | 25 x 25 / 162.2 | 3.853 | 46.24 |
| 32 mm | 32 x 32 / 162.2 | 6.313 | 75.76 |
| 40 mm | 40 x 40 / 162.2 | 9.864 | 118.37 |
Worked example
For 120 bars of 12 mm, each 6 m long, the weight per metre is 12 x 12 / 162.2 = 0.888 kg. The total length is 120 x 6 = 720 m, so the plain weight is 639.21 kg. With 10% lap and wastage it is 703.13 kg, which is 0.703 tonnes. At an example price of AED 3,000 per tonne the cost is AED 2,109.40, worked from the unrounded weight of 703.1319 kg.
Questions people ask
How do I calculate the weight of a steel bar?
Square the diameter in millimetres, divide by 162.2 to get kg per metre, then multiply by the length.
Where does 162.2 come from?
From the area of a circular bar and a steel density of about 7,850 kg/m3.
Why do some tables use 162?
It is a common rounded rule of thumb. It gives a slightly higher weight than 162.2.
Why do tables differ in the third decimal?
Different sources round the constant or the density differently, so small differences are normal.
What is the weight of a 12 mm bar per metre?
0.888 kg per metre at 162.2.
What should I put for lap and wastage?
Use the allowance your detailing and cutting plan need. The calculator does not suggest one.
Does it check the bar grade or the code?
No. It only estimates weight from diameter and length.
How do I convert kg to tonnes?
Divide by 1,000. The calculator shows both.
Does the cost include VAT?
It multiplies the price you enter by the tonnes, so it is as inclusive or exclusive of VAT as that price.
Can I replace a bar bending schedule with this?
No. A bar bending schedule lists every bar mark, shape and length. This tool is a quick estimate.