Quick Method
Start by measuring the project area. For flat surfaces, multiply length by width. If the material has depth or thickness, convert that depth to feet and multiply by the area to get cubic feet.
cubic feet = area × depth
cubic yards = cubic feet ÷ 27
What to Include
- Measured area and any openings or exclusions.
- Material depth, thickness, coverage, or yield per bag.
- Waste for cuts, compaction, breakage, overlap, or uneven ground.
- Local supplier package sizes and delivery minimums.
Common Waste Allowances
Use 5% for simple layouts, 10% for normal DIY projects, and 15% or more for irregular shapes, angled cuts, slopes, or fragile materials.
Frequently Asked Questions
What is the easiest way to estimate this?
Use the calculator linked on this page, enter measured dimensions, and round the result up to match how the material is sold.
Should I include waste?
Yes. Most projects need extra material for cuts, settling, breakage, overlap, or measurement error.
Can I use this for professional bids?
Use it for planning and cross-checking. For bids, confirm product coverage, local codes, site conditions, and supplier units.
Concrete Bag Yield Reference
| Bag Size | Approx. Yield | Bags per yd3 |
|---|---|---|
| 40 lb | 0.30 ft3 | 90 |
| 60 lb | 0.45 ft3 | 60 |
| 80 lb | 0.60 ft3 | 45 |
Example Bag Counts
A 10 × 10 ft slab at 4 inches thick is about 33.3 ft3. That is roughly 56 bags of 80-lb concrete before waste, or about 62 bags with 10% waste.