Whether you're pouring a slab, building a patio, or mixing concrete for fence posts — knowing how to calculate a yard of cement is the first step to ordering the right amount.
"A yard of cement = 27 cubic feet of volume," but how many bags do you need? How much water? And how do you account for mix ratios?
What You'll Learn
Ready to calculate your cement needs? Use our Concrete Calculator for precise calculations.
Manual Formula: How to Calculate Cement Volume in Yards
Use this simple formula:
Length × Width × Depth (in feet) ÷ 27 = Cubic Yards
📌 Example:
Pouring a slab that's 10 ft × 10 ft × 0.5 ft (6 inches deep) → 10 × 10 × 0.5 ÷ 27 = 1.85 cubic yards
Always round up to ensure you have enough mix.
Quick Reference Table: Area to Yardage
Instead of calculating from scratch every time, use this quick reference table for common project dimensions. This table shows the cubic yardage for standard square and rectangular areas at typical slab thicknesses. Remember that concrete is sold by the cubic yard, with most suppliers having a minimum order (typically 1 yard).
For example, a standard 10×10 ft patio at 4 inches thick requires approximately 1.23 cubic yards of concrete, while the same area at 6 inches thick needs 1.85 cubic yards — a 50% increase for just 2 additional inches of thickness.
| Area (ft) | Thickness (inches) | Cubic Yards |
|---|---|---|
| 10x10 | 4" | 1.23 yd³ |
| 10x10 | 6" | 1.85 yd³ |
| 12x12 | 4" | 1.78 yd³ |
| 20x20 | 6" | 7.41 yd³ |
Cement Mix Ratios Per Yard
Cement mix ratios are essential for understanding the composition needed to achieve different strengths and durability in concrete. By adjusting the quantities of cement, sand, and gravel, you can tailor the mix for your specific project needs, whether it's a simple patio or a structural foundation.
Most concrete uses a 1:2:3 mix (cement : sand : gravel).
For 1 yard of concrete mix:
| Material | Approx. Quantity |
|---|---|
| Cement | 6 x 94 lb bags |
| Sand | 1,150 – 1,250 lbs |
| Gravel | 1,700 – 1,800 lbs |
| Water | 30 gallons (approx.) |
💡 Tip: For stronger mixes (e.g. driveways), add 1–2 extra bags per yard.
How Many Bags of Cement Do I Need per Yard?
Calculating the number of bags needed per yard ensures you purchase the right amount of cement for your project. Factors such as bag size and desired mix strength influence the total number of bags. It's always wise to round up and account for additional waste to avoid shortages.
Bag Size | Bags per Yard
| Bag Size | Bags per Yard |
|---|---|
| 94 lb | 6 – 6.5 bags |
| 80 lb | 7.5 – 8 bags |
| 60 lb | 10+ bags |
Always round up and account for 5–10% waste.
Real Project Example: Shed Foundation
Let's walk through a complete real-world example to see how all these calculations work together. In this case, we'll calculate cement needed for a standard shed foundation—a common DIY project that requires accurate estimation to avoid running short or over-ordering materials.
Project specifications:
Size: 10 ft × 12 ft × 5 inches deep
Convert to feet: 5 in = 0.416 ft
Volume = 10 × 12 × 0.416 = 49.92 ft³ ÷ 27 = 1.85 yd³
Bag Count = 1.85 × 6 = ~11 bags (94 lb)
Add 1 extra bag for margin → Buy 12 bags
What Affects the Amount of Cement Needed?
Several key factors influence how much cement you'll need for your project:
- Thickness of the slab: Going from 4" to 6" increases cement needed by 50%.
- Waste buffer: Always add 5–10% to your total to account for spillage or overfill.
- Mix strength: Stronger mixes may require more cement per yard.
- Project type: Patios, sidewalks, fence posts, and foundations have different depth and strength needs.
Recommended Thickness and Strength by Project Type
| Project Type | Recommended Thickness | PSI Strength | Mix Ratio |
|---|---|---|---|
| Sidewalk | 4" | 3,000–3,500 | 1:2:3 |
| Patio | 4" | 3,000–3,500 | 1:2:3 |
| Driveway | 4–6" | 3,500–4,000 | 1:2:3 with fiber |
| Foundation | 8–10" | 3,500–4,500 | 1:2:3 or 1:2:2 |
| Fence Posts | 8–12" depth | 3,000 | 1:2:3 |
💡 Tip: For areas with freezing temperatures, increase thickness by 1–2" and consider air-entrained concrete for better durability.
Related Cement Yardage FAQs
Q: Is a yard of cement the same as a yard of concrete?
A: In casual use, yes. Technically, cement is one ingredient in concrete.
Q: How do I convert square feet to yards of cement?
A: Multiply L × W × Depth (ft) and divide by 27.
Q: How much does a yard of concrete weigh?
A: Around 4,000 lbs including all components.
Q: How many wheelbarrow loads is 1 yard of cement?
A: About 25–30 wheelbarrow loads.
Q: How many bags of cement are in a yard?
A: Roughly 6 bags (94 lb each) for a standard mix.
Use the HandyCalcs Cement Calculator
Use our free Cement Calculator to:
- ✅ Input dimensions in feet, inches, or meters
- ✅ Choose your depth and waste percentage
- ✅ See total yards and bag counts instantly
No guessing. Just accurate, fast, and flexible cement estimates for every project.
Calculate Your Cement Needs Now
Ready to start your next project? Head over to our Concrete Calculator for precise measurements and save time on your cement estimates.
Key Points Covered
- Understanding what a yard of cement is
- Using the formula to calculate cement volume
- Bags of cement needed per yard
- Cement mix ratios for different strengths
- Practical examples and instant calculator guidance