How to use the Steel Bar Weight Calculator
- 1. List the barsOne line per size: diameter in mm, length in m, number of bars.
- 2. Set density and allowance7850 kg/m³ is standard; add wastage or lap allowance if needed.
- 3. Get the weightWeight per metre, per size and the total in kg and tonnes.
Where D²/162 comes from
Weight per metre = density × area × 1 m = 7850 × (π/4) × D² / 10⁶ = D² / 162.2 kg/m, with D in mm. The thumb rule rounds this to D²/162.
So 8 mm = 0.395 kg/m, 10 mm = 0.617, 12 mm = 0.889, 16 mm = 1.58, 20 mm = 2.47 and 25 mm = 3.86 kg/m. Total weight = kg/m × length × number of bars.
Worked example and site tips
Ten 12 mm bars, 12 m long: 12² / 162 = 0.889 kg/m, × 12 m × 10 = 106.7 kg. Twenty-five 8 mm bars, 12 m long: 0.395 × 12 × 25 = 118.5 kg. Total ≈ 225 kg.
- For a bar bending schedule, include hooks, bends and laps in the cutting length.
- Actual bar weight can vary within the tolerance in IS 1786, so weigh a sample when billing matters.
- Steel rates change often; enter your supplier's rate if you want a cost.
Frequently asked questions
What is the weight of a 12 mm bar per metre?
About 0.888 kg/m (12² / 162). A 12 m bar weighs about 10.7 kg.
Is D²/162 exact?
It is a close approximation of 7850 × π/4 × D² / 10⁶, which equals D²/162.2. The difference is under 0.2%.
Can I enter a cost?
Yes. Enter your rate per kg in the optional box. No rate is assumed because steel prices change.
Is this calculator free?
Yes. You enter your name and WhatsApp number once to see your result, and all other Uncodemy tools then open without the form. Everything is calculated in your browser.