Rod formulas
| What | Formula | Example (12 mm) |
|---|---|---|
| Per metre | Dia² ÷ 162.2 | 144 ÷ 162.2 = 0.888 kg |
| Per foot | Per metre × 0.3048 | 0.888 × 0.3048 = 0.271 kg |
| One rod | Per metre × length (m) | 0.888 × 12.192 = 10.82 kg |
| Total | One rod × count | 10.82 × 5 = 54.12 kg |
| Rods per ton | 1,000 ÷ one rod | 1,000 ÷ 10.82 ≈ 92.4 |
Examples
Roof rods: 12 mm, 40 ft, 5 pieces — 40 ft = 12.192 m, 0.888 × 12.192 × 5 = ≈ 54.12 kg.
Column rods: 16 mm, 40 ft, 4 pieces — 1.578 × 12.192 × 4 = ≈ 76.97 kg.
With a price: 10 mm, 40 ft, 30 rods at Tk 95 a kg (example price) — 7.52 × 30 = 225.5 kg, cost ≈ Tk 21,422.
Weight by size (40 ft rods)
| Diameter | kg/m | kg/ft | One 40 ft rod | Per ton, about |
|---|---|---|---|---|
| 8 mm | 0.395 | 0.120 | 4.81 kg | 208 |
| 10 mm | 0.617 | 0.188 | 7.52 kg | 133 |
| 12 mm | 0.888 | 0.271 | 10.82 kg | 92 |
| 16 mm | 1.578 | 0.481 | 19.24 kg | 52 |
| 20 mm | 2.466 | 0.752 | 30.07 kg | 33 |
| 25 mm | 3.853 | 1.174 | 46.98 kg | 21 |
What to know in Bangladesh
- Rod is sold by weight: shops quote per ton or per kg, not per piece. Work out how many rods you need, get the total kg here, then match it to the per-ton price.
- Length: a standard rod is 40 ft. Contractors and shops talk in feet while drawings use millimetres and metres; the calculator takes both.
- Grade: rods are sold as 60 grade, 500 grade and so on. Grade measures strength; weight depends only on diameter and length. The engineer’s design decides the grade.
- Check the weight: some rods sold as “12 mm” are actually thinner. Weigh a few when buying and compare with this result; if they’re well under, the rod is undersized.
- How much rod a structure needs (slab, column, beam) comes from the design and bar bending schedule. This calculator weighs those rods; it doesn’t do the design.
More: where 162.2 comes from
One metre of 1 mm² mild steel (density ~7,850 kg/m³) weighs 0.00785 kg. At diameter D mm the area is πD²/4, so per metre = D² × 0.006165 = D² ÷ 162.2 kg.
In feet, 1 ft = 0.3048 m, so per foot ≈ D² ÷ 532.2 kg. Masons often say D² ÷ 533; the result is almost the same.
Rods per ton is 1,000 kg divided by the weight of one rod. Cut rods or other lengths change this number, so the calculator uses the length you enter.