Concrete Calculator
Find how much concrete you need in cubic yards, and what it will cost.
Your Details
Breakdown
Visual split of the key components
- Concrete Cost370.3703703703703
Sensitivity
How the result changes across a range
How It Works
- Enter the values on the left.
- Press Calculate to see your results and charts.
- Use Reset to start over from the defaults.
Formula Used
Concrete is priced and delivered by the cubic yard; most suppliers have a minimum order.
Good to Know
- • 4 inches is standard for driveways and patios; 6+ for heavier loads.
- • Most ready-mix suppliers have a minimum delivery quantity.
Important Notes
- • Doesn't include forms, rebar, or labor.
- • Always round up — running short mid-pour is a real problem.
Why Concrete Is Measured in Cubic Yards
Ready-mix concrete is delivered by the cubic yard because that's the standard measure mixing trucks use to load, transport, and price their loads. Converting a slab's length, width, and thickness into cubic yards is the essential step in ordering the right amount — ordering short typically means a delayed second truck arriving mid-pour, which can create a visible cold joint (seam) in the finished slab where the two pours meet and cure at different times.
Because concrete trucks are dispatched with a specific pre-mixed load, and concrete itself begins hardening on a countdown clock from the moment it's mixed, there's little room for error once a pour has started. This is very different from a material like paint or flooring where a shortfall simply means pausing to buy more — with concrete, an inaccurate estimate can mean a genuinely compromised finished result.
Always Round Up, Not Down
Most contractors and experienced DIYers add roughly 5-10% on top of the calculated volume to account for uneven ground, minor spillage, and small form imperfections that a perfectly flat theoretical calculation doesn't capture. Running short is a substantially bigger problem than having a small amount of leftover concrete, which is why it's standard practice to round up to the nearest quarter or half cubic yard rather than ordering the bare calculated minimum.
It's also worth checking your specific supplier's minimum order quantity before finalizing a small project — many ready-mix suppliers have a minimum delivery volume (often around 1 cubic yard), below which a bagged, mix-it-yourself approach may actually be more practical and cost-effective than a truck delivery.
The Basics, Defined
- Cubic yard — the standard unit ready-mix concrete is priced and delivered in, equal to 27 cubic feet.
- Slab thickness — the depth of the poured concrete; typically 4 inches for driveways and patios, more for structural or heavy-load applications.
- Cold joint — a visible seam where two separate concrete pours meet, which can occur if a project runs out of material mid-pour.
Example Case: A 20×10 Foot Patio
4-inch slab thickness, $150 per cubic yard:
Cubic yards = 66.7 ÷ 27 ≈ 2.47
Cost = 2.47 × $150 ≈ $370, rounded up to 2.5-2.75 yards for safety
Doubling the slab to 6 inches thick (for a heavier-load application, like a driveway that will support vehicles) raises the cubic yardage to roughly 3.70 — a 50% increase in material and cost purely from the added thickness, even though the footprint of the slab is unchanged.
Thickness Comparison Table
On the same 20×10 foot slab:
| Thickness | Cubic Yards |
|---|---|
| 3" | 1.85 |
| 4" | 2.47 |
| 6" | 3.70 |
Mistakes That Skew Results Ordering Concrete
- Not rounding up — running short mid-pour can create a visible cold joint where two pours meet.
- Ignoring delivery minimums — most ready-mix suppliers have a minimum order quantity worth checking before ordering a small pour.
- Underestimating thickness needs for load-bearing slabs — driveways and other heavy-load applications typically need more than the standard 4-inch patio thickness.