CALCULATION METHOD
How much concrete do I need?
Choose the pour shape, calculate its cubic volume, multiply by the number of identical pours, and add the selected allowance. The result is shown in cubic yards or cubic meters, along with whole bags and estimated truckloads.
Slab = length × width × thickness
Footing or wall = length × width × height
Round column = π × (diameter ÷ 2)² × height
Order volume = net volume × (1 + allowance)
Bags = order volume ÷ bag yield, rounded up
Concrete calculator example
A 10 × 10 ft slab at 4 inches thick contains 33.3 cu ft or 1.23 cu yd before allowance. With 10% added, the order estimate is 36.7 cu ft or 1.36 cu yd—62 bags when an 80 lb product yields 0.60 cu ft per bag.
Concrete yard calculator
Ready-mix concrete is commonly quoted by cubic yard in the US. The calculator preserves the decimal quantity so you can compare it with the supplier’s minimum order and rounding policy instead of automatically rounding to a full truck.
Concrete bag calculator
Select the exact bag size and verify its printed yield. The built-in 40, 50, 60, 80, and 90 lb options use nominal QUIKRETE Concrete Mix yields. Whole bags are rounded up after allowance.
Slabs, footings, walls, and columns
Use Slab for flat rectangular pours. Footing / wall handles any rectangular prism, including continuous footings and poured walls. Round column uses a cylinder formula for piers and columns. For a detailed slab takeoff, use the Concrete Slab Calculator; concrete masonry units and mortar belong in the Concrete Block Calculator.
Ready-mix versus bags
The cost comparison uses the same order volume. Ready-mix cost excludes delivery and short-load fees; bagged cost uses whole bags and excludes tax, mixing equipment, water, and labor. Enter current local prices before deciding.
NIST Handbook 44, Appendix C for the 27 cu ft per cubic yard conversion; QUIKRETE Concrete Mix data sheet for nominal bag yields; QUIKRETE Concrete Calculator for manufacturer calculation guidance. Accessed September 11, 2026.