Calculators › Concrete calculator

Concrete calculator

Slab, pad or round footings: get the bag count for 80, 60 or 40 lb bags and the ready-mix amount to order, with a waste margin built in.

How it works

Worked example

A 10 × 10 ft patio slab 4 in thick is 33.3 cu ft. With 10% waste that's 36.7 cu ft (1.36 cubic yards): 62 × 80 lb bags, or order 1.5 yards of ready-mix.

Tips before you buy

Bag yields are the manufacturer's published figures (Quikrete: 80 lb ≈ 0.60 cu ft). Past about 1 cubic yard (45 × 80 lb bags), ready-mix delivery or a rental mixer is usually less work. Check local code for slab thickness, reinforcement and footing depth below the frost line.

Common questions

How many 80 lb bags of concrete make a yard?

About 45. A cubic yard is 27 cu ft and an 80 lb bag yields about 0.60 cu ft.

How many bags of concrete for a 10x10 slab?

At 4 in thick, about 56 × 80 lb bags with no waste, or 62 with a 10% margin.

How thick should a concrete patio be?

4 in is standard for patios and walkways. Driveways and slabs for heavy loads are usually 5–6 in. Your local code is the authority.

More project calculators

Estimates for planning only. Product coverage and yields vary, so check the label. Last checked 2026-10-22.