Steel / TMT Bar Weight Calculator India — IS 1786 d²/162 Formula

Rule of thumb: use 1% steel of the total slab volume. For a 10m×10m×0.15m slab: volume=15 m³. Steel=1%×15×7850=1177.5 kg. For a detailed calculation, use the slab thickness divided by bar spacing × bar weight per metre.

Unit weight of steel = 7850 kg/m³ (density). For bars: weight (kg/m) = d²/162 where d is diameter in mm. Examples: 8mm=0.395 kg/m, 10mm=0.617 kg/m, 12mm=0.888 kg/m, 16mm=1.58 kg/m, 20mm=2.47 kg/m, 25mm=3.86 kg/m.

For RCC slabs: 8mm, 10mm, or 12mm bars at 150mm spacing (main bars) and 10mm at 200mm spacing (distribution bars). Minimum bar diameter for slabs is 8mm per IS 456. For heavy slabs or transfer plates, 16mm bars may be used.

As a general rule: 80–100 kg of steel per m³ of concrete for slabs, 120–150 kg/m³ for beams, 150–200 kg/m³ for columns, and 60–80 kg/m³ for footings. These are thumb rule estimates; structural design gives exact quantities.

Weight (kg) = (Diameter in mm)² ÷ 162 × Length in metres. Example: 10mm dia bar, 6m long = 10² ÷ 162 × 6 = 100/162 × 6 = 3.7 kg per bar. This formula works for all standard reinforcement bars (Fe415, Fe500, HYSD).

Fe415 (HYSD bars) — 415 MPa yield strength, most common for residential construction. Fe500 — 500 MPa, used for high-rise and industrial. Fe500D — high ductility, mandatory for earthquake-prone zones per IS 1786. Fe550 — very high strength for large infrastructure projects.

For a 300mm×300mm column with 4 bars of 16mm: number of bars×length×unit weight. If column height=3m with 40 dia laps: effective length = 3+40×0.016=3.64m. Steel = 4×3.64×1.58 (unit wt 16mm) = 23 kg per column. Add stirrups separately.

Development length is extra bar length embedded at joints for proper force transfer. Per IS 456, development length Ld = (ϕ × σs)/(4τbd). Typically 40–50 bar diameters. A 16mm bar needs 16×47 = 750mm (0.75m) development length. Add this to every bar end in your calculations.

TMT steel price in India (2026): approximately ₹55–₹75 per kg depending on grade (Fe415/Fe500), diameter, and location. Prices fluctuate with iron ore markets. Wholesale rate for 10+ tonne purchases may be ₹5–₹10 less per kg. Always get current market rates before ordering.

Per IS 456: minimum steel in slabs = 0.12% of gross cross-sectional area (for Fe415) or 0.12% for both faces. For beams: 0.85/fy minimum. For columns: minimum 0.8%, maximum 6% of gross cross-section. Typical designs use 1–3% for slabs and beams.

Number of stirrups = (beam length / stirrup spacing) + 1. For a 5m beam with 150mm stirrup spacing: (5000/150)+1 = 34 stirrups. Stirrup length = 2×(beam width + beam depth - 4×cover) + hooks. For a 300×500mm beam with 25mm cover: stirrup length ≈ 2×(250+450)+2×10d ≈ 1540mm each.

Lapping (lap splice) length = development length × 1.3. For Fe500 bars: lapping length = 45 × bar diameter. For 12mm bars: 45×12 = 540mm (minimum 0.54m). For high-stress zones, use 60d. Avoid lapping all bars at the same location — stagger laps to maintain joint strength.

Isolated square footing with main bars: bars in both directions at given spacing. Number of bars = (footing size / spacing) + 1. Multiply by bar weight per metre. Example: 1.5m square footing, 12mm bars at 150mm spacing: (1500/150)+1 = 11 bars each way = 22 bars × 1.5m × 0.888 = 29 kg.

Per IS 456, a column must have minimum 0.8% and maximum 6% of gross cross-sectional area as longitudinal steel. For a 300×300mm column: minimum = 0.8%×90000 = 720 mm² (approx 4 bars of 16mm = 804 mm²). Maximum = 6%×90000 = 5400 mm².

Main bars (tension reinforcement) carry the primary bending stress and run in the short span direction of slabs. Distribution bars are placed perpendicular to main bars, carrying nominal load, distributing stress, and controlling temperature/shrinkage cracking. Distribution bar area is typically 20% of main bar area.

For a 1000 sq ft (93 m²) ground floor slab, 125mm thick: volume = 93×0.125 = 11.6 m³. Using 1% steel: 11.6×7850×0.01 = 910 kg. At ₹65/kg market rate = ₹59,150 for slab steel alone. Add 10% for wastage, laps, and chairs = approximately 1000 kg or 1 tonne.

Retaining wall vertical bars: 12mm or 16mm at 200mm spacing on the tension face. Horizontal distribution bars: 10mm at 300mm spacing. Footing bars: 12mm or 16mm at 150mm, both ways. Design varies with wall height and soil pressure. Walls above 3m must be professionally designed.

Standard steel wastage allowance: 3–5% for standard bar bending, 5–8% for complex structures with many cuts and bends. Add 2% for laps (overlaps). In India, contractors typically add 5% wastage in billing. Always buy 5% extra to account for cutting waste on site.

For a 1200 sq ft, 2-storey residential building: approximately 4–6 tonnes of steel total including foundation, columns, beams, and slabs. Distribution: foundation 20%, columns 30%, beams 25%, slabs 25%. Exact quantity depends on structural design, soil type, and load requirements.

A steel cage for a standard 300×300mm column (4m height) with 4 bars of 16mm + 8mm stirrups at 150mm: approximately 35–40 kg of steel per column cage. At ₹70/kg = ₹2,450–₹2,800 material cost per column. Add cutting, bending labour ₹500–₹800 per cage.