Concrete Yard Calculator

Find how much concrete you need in cubic yards. See bags per yard, coverage by slab thickness, and ready-mix truck sizes for your pour.

Mason ReidFounder and Lead Estimator at MeasureThen

Last updated 2026-08-21

What Is a Concrete Yard Calculator?

A concrete yard calculator finds how much concrete you need in cubic yards, the standard unit used by ready-mix suppliers. You enter the slab length, width, and thickness, and it converts your cubic feet into cubic yards. It also helps you see coverage by thickness and match your pour to a ready-mix truck size.

How It Works

Cubic yards = Length × Width × (Thickness ÷ 12) ÷ 27.

Example

A 20 ft × 30 ft slab at 4 in thick: 20 × 30 × (4 ÷ 12) = 200 ft³ ÷ 27 = 7.41 cubic yards.

How to Calculate

Measure the slab length and width in feet. For a 20 ft by 30 ft driveway slab, enter 20 and 30.
Enter the slab thickness in inches, for example 4 in.
The calculator finds the volume in cubic feet: 20 × 30 × (4 ÷ 12) = 200 cubic feet.
Divide by 27 to get 7.41 cubic yards, the number you give your concrete supplier.
Add 5 to 10% waste yourself when ordering, since this tool returns the exact volume.

Cubic Yard Coverage by Slab Thickness

Slab Thickness	Square Feet per Yard	Notes
3 in	108 sq ft	Thin topping only
4 in	81 sq ft	Standard for patios and slabs
5 in	65 sq ft	Medium duty
6 in	54 sq ft	Driveways and heavy loads

Sources

Frequently Asked Questions

Why convert to cubic yards?

Ready-mix concrete is always ordered in cubic yards, so this is the number you give the supplier.

How many square feet does a yard cover?

One cubic yard covers 81 sq ft at 4 in thick, 108 sq ft at 3 in, or 54 sq ft at 6 in.

Should I add waste here too?

This calculator gives the exact volume. Add 5–10% yourself when ordering.

Mason ReidFounder and Lead Estimator at MeasureThen

Mason Reid founded MeasureThen after two decades of hands-on work in construction and estimating. Across residential and light commercial projects, he sized concrete pours, framed walls, hung drywall, and priced out roofing, fencing, and deck work — learning the exact math that every job depends on. At MeasureThen he writes the formulas, checks every calculator against real-world assumptions, and makes sure each one is simple enough for a homeowner to trust and a contractor to use. When he is not measuring twice, he is helping projects stay on budget.

Every MeasureThen calculator uses simple, transparent formulas and standard industry assumptions drawn from common construction practice. We show the math behind each result and include worked examples so you can follow along and double-check the numbers. Results are estimates: materials, labor, and pricing vary by region and market, so always confirm important figures with a licensed professional and your local building codes.