Concrete Calculator

⚡ Quick Concrete Calculator

Enter your slab dimensions below:

What Is a Concrete Cubic Yard?

A cubic yard is the standard unit for measuring concrete volume in the United States. One cubic yard equals 27 cubic feet or roughly 0.765 cubic metres. Ready-mix concrete is ordered by the cubic yard, and pre-mixed bags are labelled to show how many bags fill one cubic yard.

How to Calculate Cubic Yards for Concrete

Use this simple formula for rectangular slabs:

Cubic Yards = (Length × Width × Depth) ÷ 27

All dimensions must be in feet before dividing by 27. The calculator above handles unit conversion automatically.

Concrete Mix Ratios

1:2:3 Mix

Standard structural mix. Great for footings, slabs, and columns.

1:1.5:3 Mix

Stronger mix for heavy load applications and reinforced structures.

1:3:6 Mix

Lean mix for non-structural fills, blinding, and levelling.

Bag Coverage Reference

Bag Size	Yield (ft³)	Bags per Cubic Yard
40 lb	0.30 ft³	90 bags
60 lb	0.45 ft³	60 bags
80 lb	0.60 ft³	45 bags

Pro Tips

Always add 5–10% extra to your order to account for spillage and uneven sub-base.
For pours over 1 cubic yard, consider ordering ready-mix concrete — it's cheaper per yard than bags.
Cure concrete for at least 7 days by keeping it moist before applying any load.
In cold weather (below 40°F / 4°C), use a concrete blanket or heated enclosure to prevent freezing.

Frequently Asked Questions

How many bags of concrete make a cubic yard?

It takes approximately 45 bags of 80 lb concrete, 60 bags of 60 lb, or 90 bags of 40 lb to fill one cubic yard (27 cubic feet).

How deep should a concrete slab be?

A standard residential slab is typically 4 inches (10 cm) thick. Driveways should be 4–6 inches, and structural slabs for garages or heavy loads need 6+ inches.

Can I mix concrete myself for a large pour?

For pours under 0.5 cubic yards, DIY mixing is practical. Above that, renting a mixer or ordering ready-mix concrete saves significant time and effort.