Slab Load Calculator

How it works

self-weight = thickness × concrete unit weight · D = self-weight + superimposed dead load · wu = max(1.4D, 1.2D + 1.6L) (ASCE 7 / ACI 318) · 1 kN/m² = 101.97 kg/m² = 20.885 psf

A floor slab carries its own weight, the superimposed dead load of finishes, ceilings, services and partitions, and the live load from people and contents. Reinforced concrete weighs about 24 kN/m³ (2,400 kg/m³), so every centimetre of slab adds 0.24 kN/m² (24.5 kg/m²). Minimum uniform live loads come from ASCE 7 Table 4.3-1 (similar values appear in most national codes). For strength design ACI 318 and ASCE 7 combine them as 1.2D + 1.6L, or 1.4D where dead load dominates; the unfactored service load D + L is used for deflection and for footing sizes.

Worked example

A 12 cm residential slab with 1.5 kN/m² of finishes and partitions: self-weight = 0.12 × 24 = 2.88 kN/m²; D = 2.88 + 1.5 = 4.38 kN/m²; L = 1.92 kN/m². Factored load = 1.2 × 4.38 + 1.6 × 1.92 = 5.26 + 3.07 = 8.33 kN/m² (849 kg/m²), which governs over 1.4D = 6.13 kN/m². Service load D + L = 6.30 kN/m².

Sources: ASCE/SEI 7-22 Minimum Design Loads — Table 4.3-1 and §2.3 load combinations · ACI 318-19 §5.3 — Load factors and combinations

Frequently asked questions