- No data uploaded
- Instant results
How Much Concrete for a 20x20 Slab?
A 20 × 20 ft slab at 4 in thick needs 5.43 yd³ (146.7 ft³ · 4.15 m³ incl. 10% waste).
How Much Concrete for a 20x20 Slab?
Concrete needed146.7 ft³ · 4.15 m³ incl. 10% waste
80 lb bags (0.60 ft³ each)
245
60 lb bags (0.45 ft³ each)
326
40 lb bags (0.30 ft³ each)
489
Ready-mix trucks (~9 yd³)
0.6
Ready-mix suppliers usually sell in ¼ or ½ yd³ steps with a minimum order. Slabs on grade are typically 4 in for patios/walks and 5–6 in for driveways.
Planning estimates only. Building codes, loads and material specs vary — have a licensed engineer or contractor confirm quantities and safety requirements. Disclaimer
By thickness
- 4 in: 5.43 yd³
- 5 in: 6.79 yd³
- 6 in: 8.15 yd³
- 8 in: 10.86 yd³
Frequently asked questions
Is my data uploaded?
No. The calculation runs entirely in your browser — nothing you type is sent to a server.
Is it free?
Yes — free, unlimited and no sign-up.