Before you pour a slab, you need to know how much steel reinforcement (rebar or TMT bars) to order. Too little and you have a structurally inadequate slab. Too much and you're wasting money. This guide gives you the practical numbers for a 1,000 sq ft RCC slab — with the formula so you can scale it to any size.
Quick Answer: Steel for a 1,000 Sq Ft Slab
For a standard residential RCC slab of 1,000 sq ft (approximately 93 m²) at 4-inch (100mm) thickness using M20 concrete and Fe500 TMT bars:
- Steel required: approximately 750–900 kg
- This works out to roughly 0.8–1% of the concrete volume as steel by weight — the standard reinforcement ratio for residential two-way slabs
This figure assumes:
- Two-way RCC slab (reinforcement in both directions)
- 10mm dia bars at 150mm spacing in both directions (main + distribution steel)
- No cantilever, beam, or heavy point loads
- Slab span within 3–4m supported on all four sides
Step-by-Step Calculation
Step 1: Calculate concrete volume
- Area: 1,000 sq ft = 92.9 m²
- Thickness: 4 inches = 0.1 m
- Volume: 92.9 × 0.1 = 9.29 m³
Step 2: Apply reinforcement ratio
Standard residential slab reinforcement ratio: 0.7–1.0% of concrete volume
- Steel volume: 9.29 × 0.008 (0.8%) = 0.0743 m³
- Steel weight: 0.0743 × 7,850 kg/m³ (density of steel) = ~583 kg
Add 10% for laps, wastage, chairs, and binding wire: 583 × 1.10 = ~641 kg
With additional steel for beams along slab edges (typical in Indian RCC construction), total site delivery is commonly 750–900 kg for a 1,000 sq ft slab.
Steel Requirement by Bar Diameter and Spacing
| Bar Dia | Spacing | Steel Weight (kg/m²) | For 1,000 sq ft (93 m²) |
|---|---|---|---|
| 8mm | 150mm both ways | 5.3 kg/m² | ~493 kg |
| 10mm | 150mm both ways | 8.2 kg/m² | ~763 kg |
| 10mm | 125mm both ways | 9.9 kg/m² | ~920 kg |
| 12mm | 150mm both ways | 11.8 kg/m² | ~1,097 kg |
| 12mm + 8mm | 150mm (main + dist.) | 10.0 kg/m² | ~930 kg |
The structural engineer's drawing will specify the exact bar size and spacing. Never deviate from the drawing — reducing bar size or increasing spacing weakens the slab structurally.
How to Calculate Steel Bar Weight
The weight per metre of a TMT bar is calculated using this formula:
Weight (kg/m) = (D² ÷ 162), where D is the diameter in mm.
- 8mm bar: 8² ÷ 162 = 0.395 kg/m
- 10mm bar: 10² ÷ 162 = 0.617 kg/m
- 12mm bar: 12² ÷ 162 = 0.888 kg/m
- 16mm bar: 16² ÷ 162 = 1.580 kg/m
- 20mm bar: 20² ÷ 162 = 2.469 kg/m
Steel Costs by Country
| Country | TMT/Rebar Grade | Price per kg | Steel cost for 1,000 sq ft slab (~800 kg) |
|---|---|---|---|
| India | Fe500 TMT | ₹58–₹72/kg | ₹46,400–₹57,600 |
| UAE | Grade 60 / BS4449 | AED 3–4.5/kg | AED 2,400–3,600 |
| UK | B500B (BS4449) | £0.80–£1.20/kg | £640–£960 |
| USA | Grade 60 (ASTM A615) | $0.80–$1.30/kg | $640–$1,040 |
| Australia | 500N (AS/NZS 4671) | A$1.20–A$2.00/kg | A$960–A$1,600 |
Pro Tip: Always get a Bar Bending Schedule (BBS) from your structural engineer before ordering steel. The BBS lists every bar, its size, length, shape, and quantity — so you order exactly what you need with no guesswork. Ordering without a BBS usually means you either over-order (waste) or run short (delay).
Steel for Other Structural Elements
| Element | Typical Reinforcement Ratio | Bar Sizes Used |
|---|---|---|
| RCC slab | 0.7–1.0% of concrete volume | 8mm, 10mm, 12mm |
| RCC beam | 1.0–2.5% | 12mm, 16mm, 20mm main bars; 8mm stirrups |
| RCC column | 1.0–4.0% | 12mm, 16mm, 20mm main bars; 8mm ties |
| Foundation footing | 0.12–0.3% | 10mm, 12mm |
| Retaining wall | 0.3–0.6% | 12mm, 16mm |
For our complete breakdown of steel grades and standards, including TMT bar grades (Fe415, Fe500, Fe550) and how they compare to BS and ASTM grades, see our guide on TMT bar vs rebar grades and standards. For calculating steel specifically for slabs, our detailed guide on how to calculate steel for a slab walks through every step.
