Calculator

Concrete Calculator

Slab, footing, or post-hole — enter dimensions and depth. Output: cubic yards, plus the exact number of 60 lb (0.45 cu ft) or 80 lb (0.6 cu ft) bags. Built-in 10% overage.

~150 lb/ft³ 4" default depth 0.6 cu ft bags

Pick a shape

step 1 of 3

Area: 80 sq ft

Enter measurements

step 2 of 3

Length (ft)

Width (ft)

Depth (in)

Options

step 3 of 3

Bag size

+10% settling buffer Concrete settles after a few rains. Recommended on.

Cost compare (bulk vs bagged)

Bulk $ / cu yd

Bag price ($)

Edit defaults — bulk delivery + bag pricing varies wildly by region.

You need

0 bags

0.6 cu ft each

Cubic yards

Cubic feet

Cubic meters

Cost compare

Bulk $174

Bagged $294

Bulk saves $120 for this project.

Density assumption

Standard concrete is ~4050 lb/yd³ (150 lb/ft³). An 80 lb bag yields ~0.6 cu ft; a 60 lb bag yields ~0.45 cu ft.

Tip: Pour at 50-90°F. Cold pours need accelerator + curing blanket; hot pours need retarder + shading. Don't pour in rain.

Common concrete projects

Pick a typical project to see what shape & depth to use in the calculator above.

Slab — 4" thick

Walkway, patio pad, AC pad

Setup: rectangle, 4" depth

Slab — 6" thick

Driveway, garage floor

Setup: rectangle, 6" depth

Footing

Continuous footing under wall or post

Setup: rectangle, 12" depth

Post-hole

Fence post or deck pier (use Circle)

Setup: circle, 30" depth

60 lb bag

0.45 cu ft

~60 bags per yd³

80 lb bag

0.60 cu ft

~45 bags per yd³

Truck min

~1 yd³

Below 1 yd³ — buy bagged.