Calculate weight and quantity of steel reinforcement bars by diameter.
A steel rebar calculator estimates the total weight of reinforcement steel required for a slab, beam, column, or footing. Reinforced concrete derives its tensile strength from embedded steel bars; concrete itself is strong in compression but weak in tension, while steel is strong in both.
Rebar is specified by diameter (in mm, e.g. 8 mm, 12 mm, 16 mm, 20 mm, 25 mm) and grade (Fe415, Fe500, Fe550 in India — the number is the yield strength in N/mm²). Fe500 is the modern standard for most structural concrete. Steel is sold by weight per linear metre — derived from the bar diameter using the standard density of 7,850 kg/m³.
W = \frac{d^2}{162.2} \text{ kg/m}
Inputs: 10 m² slab with main reinforcement 12 mm @ 150 mm c/c both ways · Slab depth 125 mm
Fe500 is the standard for most residential and commercial RCC work in India and is widely available. Fe550 has 10% higher yield strength, allowing slightly less steel for the same load — but availability is limited and the cost per kg is higher. For most residential projects, Fe500 is the safe, economical choice; specify Fe550 only when the structural engineer's design requires it.
Concrete cover protects rebar from corrosion. Standard values per IS 456: 20 mm for slabs, 25 mm for beams and columns, 40 mm for footings, 50 mm for foundations in aggressive soil. In coastal areas with high salinity, add 10 mm extra cover. Insufficient cover is the single biggest cause of premature concrete deterioration.
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