How to Calculate Concrete Yards (Formula)
Length(ft) x Width(ft) x Depth(ft) / 27. Example: 20x20x0.33 / 27 = 4.8 yards.
How to Calculate Concrete Yards: Simple Formula Guide
Ordering the right amount of concrete is critical. Too little, and you're scrambling for more mid-pour. Too much, and you're paying for concrete you can't use. This guide shows you the simple formula to calculate exactly how many cubic yards you need.
The Basic Formula
Length (feet) × Width (feet) × Depth (feet) ÷ 27 = Cubic Yards
That's it. This formula works for any rectangular or square area. The key is converting everything to feet and using the correct depth.
Step-by-Step Calculation
Step 1: Measure Length and Width
Measure your area in feet. For example, a 20x20 foot driveway.
Step 2: Determine Depth
Convert depth to feet. Common depths:
- 4 inches = 0.33 feet (4 ÷ 12)
- 5 inches = 0.42 feet (5 ÷ 12)
- 6 inches = 0.5 feet (6 ÷ 12)
Step 3: Apply the Formula
Multiply length × width × depth, then divide by 27.
Real-World Examples
Example 1: Standard Driveway
Dimensions: 20 feet × 20 feet × 4 inches thick
Calculation: 20 × 20 × 0.33 ÷ 27 = 4.89 cubic yards
Order: 5 cubic yards (always round up slightly)
Example 2: Patio
Dimensions: 12 feet × 16 feet × 4 inches thick
Calculation: 12 × 16 × 0.33 ÷ 27 = 2.35 cubic yards
Order: 2.5 cubic yards
Example 3: Garage Floor
Dimensions: 24 feet × 24 feet × 6 inches thick
Calculation: 24 × 24 × 0.5 ÷ 27 = 10.67 cubic yards
Order: 11 cubic yards
Why Divide by 27?
There are 27 cubic feet in 1 cubic yard (3 feet × 3 feet × 3 feet = 27). Dividing by 27 converts cubic feet to cubic yards, which is how concrete is sold.
Accounting for Waste
Always add 5-10% to your calculation for waste, spillage, and over-excavation. It's better to have a little extra than to run short mid-pour.
Example: If you calculate 4.89 yards, order 5.25-5.5 yards to account for waste.
Irregular Shapes
For irregular shapes, break them into rectangles, calculate each, then add them together.
Example: An L-shaped patio. Calculate each rectangle separately, then add the totals.
Common Mistakes
1. Forgetting to convert inches to feet: 4 inches is 0.33 feet, not 4 feet
2. Not accounting for waste: Always add 5-10%
3. Measuring incorrectly: Measure the actual pour area, not the overall space
4. Forgetting thickness variations: If some areas are thicker, calculate separately
Online Calculators
Many online calculators can do this for you, but understanding the formula helps you verify the results and catch errors.
The Bottom Line
Calculating concrete yards is simple: Length × Width × Depth (in feet) ÷ 27. Always convert depth from inches to feet, add 5-10% for waste, and round up to the nearest 0.25 yards when ordering.
Getting the right amount prevents costly delays and waste. Use this formula, double-check your math, and you'll order the correct amount every time.
Need help calculating your concrete needs? Contact Local Concrete Contractor. We'll calculate the exact amount needed for your project and ensure you get the right quantity delivered.
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