Rebar Weight Calculation
Weight = D²/162.2 kg/m where D is dia in mm
Rebar weight is the mass per unit length of a steel reinforcement bar, used for procurement, BBS preparation, and quantity surveying. The standard formula for any round steel bar is weight (kg/m) = d² ÷ 162.2, where d is the nominal diameter in millimetres. The constant 162.2 is derived from the cross-sectional area (πd²/4) multiplied by steel density (7850 kg/m³) and divided by 10⁶ to convert mm² to m². Indian Standard IS 1786:2008 (HYSD bars Fe415/Fe500/Fe550/Fe550D/Fe600) specifies the nominal mass per metre and mass tolerances for each diameter.
For common Indian bar sizes, the values are: T6 = 0.222, T8 = 0.395, T10 = 0.617, T12 = 0.888, T16 = 1.580, T20 = 2.466, T25 = 3.853, T28 = 4.834, T32 = 6.313, T36 = 7.990, T40 = 9.864, T50 = 15.413. These are nominal (theoretical) values — actual weight may deviate by ±3% to ±7% depending on diameter per IS 1786 Table 4 (smaller bars have larger tolerance because surface deformations contribute relatively more mass). Rolled-steel mills often supply bars at the lower tolerance limit to reduce material cost — a 12 m T16 bar at −3% tolerance weighs 1.532 kg/m instead of 1.580.
For a procurement engineer, rebar weight drives ₹/MT pricing. At ₹65,000/MT current Indian rebar pricing (April 2026), a 100-tonne BBS variance is ₹65 lakh of project cost. Always procure on weight basis (₹/kg or ₹/MT), not piece basis (₹/bar) — the latter penalises the buyer when mills supply at the upper tolerance limit. For a 28-day turn-around residential project, accurate rebar weight calculation prevents both shortage delays and excess inventory carrying cost.
- BBS preparation — multiply cutting length by unit weight for total weight
- Procurement — total tonnage by diameter for material requisition
- Quantity surveying — billing reconciliation against received tonnage
- Tendering — basis for steel rate-per-MT calculation
- Inventory management — converting bar count to weighbridge tonnage