Quick answer
Multiply length by width by thickness to get cubic feet, then divide by 27 to convert cubic feet to cubic yards. Convert thickness from inches to feet before multiplying.
Step by step
- Measure length and width. Use feet for both dimensions.
- Convert thickness to feet. Divide inches by 12.
- Find cubic feet. Multiply length × width × thickness in feet.
- Convert to cubic yards. Divide cubic feet by 27, then add a project allowance before ordering.
Formula or rule of thumb
Example
A 12 ft × 10 ft slab at 4 in thick is 12 × 10 × 0.333 ÷ 27 ≈ 1.48 yd³ before any waste allowance.
Common mistakes
The most common errors are leaving thickness in inches, forgetting to divide by 27, and ordering the exact geometric amount with no allowance for site variation or spillage.
Planning note: product yields, installation methods, site conditions and local requirements can change the final quantity. Use the exact manufacturer or supplier information before purchasing.
Decision guide
| Decision point | What the estimate tells you | What to verify |
|---|---|---|
| Measurements | Start with accurate project dimensions and the correct units. | Replace generic assumptions with site measurements. |
| Product data | Use the actual package yield, coverage or density. | Check the current manufacturer or supplier label. |
| Final decision | Treat the result as an early planning estimate. | Confirm final quantities and requirements before purchase. |
Authority and verification
RenoMetric provides transparent planning arithmetic, not a structural design or contractor quote. Verify final decisions with the current product label or supplier data, the applicable local requirements, and a qualified professional when the project is safety-critical.
- RenoMetric methodology — formulas, units and planning limitations.
FAQ
Why divide by 27?
One cubic yard contains 27 cubic feet.
Should I round concrete up?
Concrete is normally ordered with a project-specific allowance rather than to the exact geometric decimal.
Can I use this for irregular shapes?
Split the project into simple measurable sections, calculate each section, then add them together.