Pick the bar diameter, enter length and count, and get the weight in kilograms — steel is bought by weight but used by length, and this is the conversion every site does daily.
The formula
weight (kg/m) = diameter² ÷ 162.28
With the diameter in millimetres. Multiply by bar length in metres and the number of bars for total weight. The chart above the fold lists every standard diameter per metre and per full-length 12 m bar.
Ordering tips
Steel is quoted per kg or per tonne, but bar-bending schedules count pieces and cut lengths — always convert both ways before ordering. Add 3–5% for laps, hooks, bends and cutting wastage on top of the schedule quantity; laps alone consume roughly one diameter-dependent extra bar in every 15–20.
What this page deliberately does not do: tell you what diameter or how many bars a beam, column or slab needs. That is structural design, and it belongs to a licensed engineer working from your drawings — not to any calculator.
Frequently asked questions
What is the weight of an 8 mm TMT rod per metre?
8 × 8 ÷ 162 ≈ 0.395 kg per metre, so a standard 12 m bar weighs about 4.74 kg. A one-tonne lot is roughly 211 bars.
How is the d²/162 formula derived?
Steel density is 7,850 kg/m³. Working through the area of a circular bar (π/4 × d²) with d in millimetres and length in metres, the constant collapses to d² ÷ 162.28. It applies to any circular mild-steel or TMT bar.
How many 12 mm bars are in one tonne?
A 12 mm bar weighs 0.888 kg/m, so a 12 m bar is about 10.65 kg — roughly 94 bars per tonne.
Why does my delivered weight differ slightly from the formula?
IS 1786 permits a tolerance on mass per metre (±7% for smaller diameters, ±5% and tighter for larger ones), and rolled bars run within it. Small differences between the chart and the weighbridge are normal; large ones are worth questioning.
Reviewed on 15 August 2026. These are preliminary planning quantities from standard methods — actual consumption varies with workmanship, wastage and site conditions. VastuCalc does not provide structural design; sizes, grades and reinforcement must come from a qualified engineer.