| Primary value | 2.0 to 3.0 % of cross-section (≈ 160–235 kg / m³) |
| Applies to | Tied and spirally-reinforced RCC columns · Residential and commercial framing · Estimation of steel quantity at tender stage |
| Exceptions | IS 456 minimum (main reinforcement) → 0.8% of gross area |
| IS 456 maximum (general) → 6.0% of gross area | |
| IS 456 maximum at lap location → 4.0% of gross area | |
| Heavily loaded ground-floor column (G+10+) → 3.5–4.0% | |
| Measured as | Sum of all longitudinal bar areas ÷ gross column cross-section × 100. By weight: 2.5% = 196 kg of steel per m³. |
| Source | IS 456 — Clause 26.5.3 ✓ Verified |
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Columns are axial-load members — the steel works hardest here. 2–3% covers most residential framing; below the IS 456 floor of 0.8% the column behaves as plain concrete and ductility collapses in earthquake. Above 4% (or 6% absolute) bar congestion makes proper concrete placement impossible.
Detailed designers target 2.5% for typical G+3 to G+5 buildings — high enough to handle moment-frame demand, low enough that 4 main bars and 8 mm ties fit cleanly. Tall buildings step the % down with height as axial load drops.