Steel Quantity for Slab Calculator – RCC Slab Reinforcement
Calculate the exact steel reinforcement quantity for RCC slabs — main bars along the length and distribution bars along the width. Gives total weight in kg and tonnes including wastage.
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Steel Calculation Formula for Slab
No. of Main Bars = (Slab Width − 2×Cover) / Spacing + 1 Length of Each Bar = Slab Length + 2×(40d development) Total Length = No. of Bars × Bar Length Weight (kg) = Total Length × D² × 0.00617 / 100
5m × 4m slab, 12mm @ 150mm, 8mm @ 200mm: Main bars: 27 nos × 5.96m = 161m → 143 kg Dist. bars: 34 nos × 4.96m = 169m → 67 kg Total = 210 kg (with 5% wastage = 220 kg)
Thumb Rule for Steel in RCC Slab
1% steel ratio
~80 kg/m³
Thumb rule
4–5 kg/sq ft
Per m² (avg)
40–50 kg/m²
Frequently Asked Questions
As a thumb rule, 4–5 kg of steel per sq ft is used for RCC slabs. For 1000 sq ft: approximately 4,000–5,000 kg (4–5 tonnes) of steel. The exact quantity depends on slab thickness, bar diameter, and spacing as designed by the structural engineer.
As per IS 456:2000, the minimum reinforcement in a slab shall not be less than 0.15% of total cross-sectional area for Fe 250 steel and 0.12% for Fe 415/500 HYSD bars.
Typically 8mm, 10mm, or 12mm HYSD Fe 415/500 bars are used as main bars and distribution bars in residential RCC slabs. Heavier slabs may use 16mm bars.