Concrete Slab Calc

Concrete calculator

Enter the dimensions of your pour and get cubic yards, bag counts and an estimated cost.

Enter your dimensions

ft

ft

in

%

cu yd

A Slab with each measurement the calculator asks for marked on it, so it is clear which dimension goes in which box.WidthLengthThickness

What you need

4.94 cu yd

Cubic feet
133.33 cu ft
Cubic metres
3.776
Order this much
5.43 cu yd
80 lb bags
245
60 lb bags
326
Weight
18,670 lb
Truckloads
1
Cost
$850 to $1,150

Common sizes

Common sizes
Size Area Cubic yards 80 lb bags
10×10 100 cu ft 1.23 62
20×20 400 cu ft 4.94 245
30×40 1,200 cu ft 14.81 734
20×30 600 cu ft 7.41 367
30×30 900 cu ft 11.11 550
12×12 144 cu ft 1.78 89
40×60 2,400 cu ft 29.63 1,467
30×50 1,500 cu ft 18.52 917

the slab size list

Concrete calculators

How this is worked out

volume in cubic feet = width in feet × length in feet × thickness in inches ÷ 12

cubic yards = cubic feet ÷ 27

bags = cubic feet with waste ÷ what one bag yields, rounded up

At the dimensions above that is 133.33 cubic feet, which is 4.94 cubic yards.

Where these numbers come from

Bag yields: QUIKRETE Concrete Mix data sheet No. 1101. Price basis: Concrete Financial Insights weighted average selling price for 2025, escalated with U.S. Bureau of Labor Statistics PPI series PCU327320327320 (2026-06). Prices vary by region — enter your own quote above.