Concrete Volume Converter

Concrete volume conversions use cubic feet as the base unit.

Volume conversions:

• 1 cubic yard = 27 cubic feet
• 1 cubic meter = 35.3147 cubic feet
• 1 cubic yard = 0.764555 cubic meters

Concrete bag yields (approximate):

• 60 lb (27 kg) bag = 0.45 cubic feet (0.0127 cu m)
• 80 lb (36 kg) bag = 0.60 cubic feet (0.017 cu m)

Bags per cubic yard:

• 60 lb bags: 60 bags per cubic yard
• 80 lb bags: 45 bags per cubic yard

Common project sizes:

• Sidewalk (4 ft × 20 ft × 4 in): ~0.99 cu yd (0.76 cu m)
• Patio slab (10 × 10 ft × 4 in): ~1.23 cu yd (0.94 cu m)
• Fence post hole (10 in diameter × 3 ft): ~1.6 cu ft (0.045 cu m)

Tip: Always order 5-10% extra to account for waste and spillage.

That cushion isn’t padding for its own sake. Real forms are never perfectly even, the subgrade dips, some concrete clings to the wheelbarrow, and running short mid-pour is a genuine problem: a cold joint forms where the first batch sets before the next one arrives, leaving a weak seam through the slab. Leftover concrete is far cheaper than a failed pour, so round up rather than down.

There’s also a crossover point worth knowing. Mixing bags by hand is fine for a few post holes or a small pad, but once you’re past roughly one cubic yard (27 cubic feet, or about 45 of the 80-pound bags), the labor and the risk of inconsistent batches make a ready-mix truck the better call. The thickness trap catches beginners: slab depth is given in inches while length and width are in feet, so a 4-inch slab is 0.33 feet thick, not 4. Convert it before multiplying, or your volume comes out twelve times too big.