Concrete Calculator

Length × width × thickness gives the volume in cubic feet (after converting thickness from inches to feet), and dividing by 27 (the number of cubic feet in a cubic yard) converts that to cubic yards — the standard unit concrete is typically ordered in by the truckload.

That's the manufacturer-published yield for a standard 80 lb bag of pre-mixed concrete once water is added — it's a commonly cited figure across major concrete mix brands, though you should always check your specific bag's label since yields can vary slightly by product.

The bag count is rounded up to the next whole bag, but doesn't add an extra buffer percentage for spillage, uneven sub-grade, or over-excavation — many contractors add 5-10% extra material to the calculated volume for exactly that reason.

Yes — the same length × width × thickness volume math works for any rectangular concrete pour; for round post holes, calculate the cylindrical volume separately (π × radius² × depth) and convert to cubic yards the same way.