Concrete Calculator — Cubic Yards & Bags
Calculate concrete volume for a slab or footing in cubic yards, metres and feet, plus how many 40/60/80 lb bags you need. Free, in your browser.
🔒 Calculated in your browser. Bag yields (40/60/80 lb) are typical — check your product. Add a waste % for spillage and uneven subgrade.
Volume and bag count
Enter the length and width in feet and the thickness in inches for a slab or footing. The tool returns the volume in cubic feet, cubic yards and cubic metres, and estimates the number of pre-mix bags for the size you pick (40, 60 or 80 lb). Add a waste percentage for spillage and uneven ground.
Order a little extra
Bag yields are typical values — always check your product, and remember that sub-base variation and spillage mean you usually want a small buffer. For large pours, ready-mix by the cubic yard is often cheaper than bags. Everything runs in your browser.
Frequently asked questions
How many bags of concrete do I need?
Divide the volume in cubic feet by the bag yield (about 0.6 ft³ for an 80 lb bag, 0.45 for 60 lb, 0.3 for 40 lb) and round up. The tool does this for you.
How do I convert to cubic yards?
Cubic yards = cubic feet ÷ 27. The tool shows cubic feet, yards and metres at once so you can order whichever way your supplier prices it.