How to Use the Concrete Volume Calculator
Miscalculating concrete volume for a slab or driveway pour can mean running short mid-pour, which creates a weak cold joint, or ordering too much and wasting money. This calculator takes the width, length, and thickness of your pour area to calculate the base volume in cubic yards, then adds your waste margin and estimates how many mixer truck loads you'll need.
For example, a 30ft x 20ft slab at 4in thick works out to 200 cubic feet, or about 7.41 cubic yards. Adding a 5% margin brings that to roughly 7.78 cubic yards. Since a standard concrete mixer truck carries about 10 cubic yards, this pour needs just 1 truck load.
Real pours typically need more concrete than the raw math suggests, due to subgrade irregularities, formwork variance, and spillage. Adding a 5-10% waste margin is standard practice. Truck capacity and dispatch minimums vary by supplier, so confirm exact load sizes with your ready-mix provider.
Frequently Asked Questions
A standard concrete mixer truck typically carries about 10 cubic yards. Dividing your required volume by that figure ahead of time tells you how many truck loads to order, avoiding a shortage or excess on pour day.
To account for subgrade irregularities, formwork variance, and spillage during the pour, adding a 5-10% margin to your calculated volume is standard practice.