About

Pouring a concrete slab is a major project where the cost of materials is the biggest variable. Ordering short means an expensive second delivery and a structural weak point; ordering too much is money down the drain. This calculator is designed to provide professional-grade estimates for rectangular slabs.

It includes a specialized feature for Monolithic Slabs (slabs with thickened edges), which are common in garages and sheds where the perimeter acts as a footing. By accounting for the extra concrete in the edges, this tool prevents the common underestimation error that occurs when using simple LxWxH formulas.

Formulas

Basic Slab:

V_slab = L × W × T

Thickened Edge (Monolithic):

V_edge = Perimeter × W_edge × (D_total − T_slab)

Total Volume = V_slab + V_edge.

Reference Data

Slab Thickness	Application	Sq. Ft per Cubic Yard	Notes
4 inches	Sidewalks, Patios, Garage Floors	81 sq. ft.	Standard Residential
5 inches	Driveways (Light Duty)	65 sq. ft.	Prevent cracking
6 inches	Driveways (Heavy), Sheds	54 sq. ft.	Heavy loads
8 inches	Commercial / Industrial	40 sq. ft.	Forklift traffic
Edge Beam	Perimeter Support	Varies	Requires extra 20-30%
Truck Load	Standard Mixer	9 - 10 cu. yds.	Max capacity
Small Load	Short Load	1 - 4 cu. yds.	Often extra fee
Curing Time	Full Strength	28 Days	Walkable in 24-48h

Frequently Asked Questions

A thickened edge (or turned-down edge) is a structural perimeter added to a slab. It acts like a footing to support walls or heavy vehicle loads at the edge of the concrete, usually 8-12 inches deep compared to the 4-inch center.

A standard ready-mix truck can hold between 9 and 10 cubic yards. However, fully loaded trucks are very heavy; sometimes load limits restrict them to 8 yards.

Yes, for indoor slabs or garages, a vapor barrier (plastic sheeting) under the concrete prevents ground moisture from wicking up through the porous concrete.

Rule of thumb: If you need more than 1 cubic yard (approx 45 bags of 80lb), it is usually cheaper and much easier to order a truck.