Calculate how much concrete you need for slabs, footings, columns and walls in cubic yards or metres.
Pick the shape you are pouring — slab, footing (strip foundation), wall or column — then enter the dimensions in feet/inches or metres/millimetres. The tool returns the volume in cubic yards and cubic metres, plus how many pre-mixed bags you would need if you are not ordering ready-mix (called “ready-mixed” or “volumetric” concrete in the UK).
| Job | US | Metric |
|---|---|---|
| Shed / patio base | 4 in | 100 mm |
| Driveway / garage | 6 in | 150 mm |
| Footing / foundation | 8–12 in | 200–300 mm |
A 10 ft × 12 ft slab at 4 in deep = 10 × 12 × 0.333 = 40 ft³ ≈ 1.48 yd³. Add 10% waste ≈ 1.63 yd³. In metric that is about 1.24 m³.
Tip: always round up and order a little extra — you cannot easily add fresh concrete to a pour that has already started to set. A 60 lb bag yields ≈ 0.45 ft³; an 80 lb bag ≈ 0.60 ft³; a 25 kg bag ≈ 0.012 m³.
A 10 ft × 10 ft slab at 4 inches deep needs about 1.24 cubic yards of concrete, or roughly 1.36 cubic yards with 10% waste.
About 60 standard 60 lb bags or 45 standard 80 lb bags make one cubic yard.
Yes – 5-10% for simple slabs and up to 15% for irregular shapes or footings with forms.
A typical garden or shed slab is 100 mm (4 in); driveways and areas taking vehicles usually need 150 mm (6 in) with reinforcement.
For small jobs bagged or site-mixed concrete is usually cheaper; for more than about a cubic metre, ready-mix delivery is often better value and faster.
