How many bags of concrete do I need?
Enter the slab size and thickness. You get the volume and how many bags of pre-mixed concrete to buy.
Your project
4 in for patios and walks
What to buy
Bags to buy
62 bags of 80 lb
- Volume
- 36.7 cu ft (1.36 cubic yards), including 10% extra
- Yield per bag
- 0.6 cu ft for a 80 lb bag
Above about 1 cubic yard, ordering ready-mix is usually cheaper and far less work than mixing bags.
See mixing tubs on Amazon
Also useful: Finishing trowels · Bull floats
How it’s calculated
Volume is length times width times thickness (inches divided by 12), plus a margin for spillage and uneven ground. 10% is a common allowance.
Bag yields as printed on standard pre-mixed bags: 40 lb makes about 0.3 cu ft, 60 lb makes about 0.45 cu ft, 80 lb makes about 0.6 cu ft.
Patios and walkways are usually 4 inches thick; slabs that carry vehicles are thicker and need reinforcement. Check local requirements.