Concrete Calculator
Calculate the cubic yards of ready-mix concrete needed for a slab, footing or patio, plus the number of 80 lb bags if you are mixing by hand.
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Estimated cost
$240 – $329
Typical figure around $284.
- Slab area
- 144 sq ft
- Concrete volume
- 1.78 cu yd
- 80 lb bags (if mixing)
- 80 bags
Order 5–10% more than the calculated volume to cover spillage and uneven subgrade.
Planning estimate only — confirm quantities with your supplier or contractor before ordering.
How this estimate is calculated
The estimate is built from length (ft), width (ft), thickness (in) and mix, then priced at national average rates. It reports slab area, concrete volume and 80 lb bags (if mixing), with quantities rounded up so you are never short of material and the standard waste allowance already included where it applies.
Order 5–10% more than the calculated volume to cover spillage and uneven subgrade.
The dollar range is a national average, so treat it as a starting point rather than a bid. Labor rates, permit fees and material delivery differ by region — the state table below shows how your state compares, and construction cost by state breaks the picture down further.
Prefer the longer version? Read our guide to How much does a fence cost to install and How much does a pool fence cost.
Cost by mix
Each row prices the same default job shown in the calculator above, changing only the mix. Use it to see what the upgrade or the cheaper option really costs before you commit.
| Mix | Low | High |
|---|---|---|
| Ready-mix delivery | $240 | $329 |
| Bags mixed on site | $338 | $462 |
What the same job costs by state
Every row applies that state's construction cost index to the national range calculated above. The index bundles local labor rates, permit fees and material delivery, so it is a planning figure rather than a bid.
| State | Index | Low | High |
|---|---|---|---|
| Ohio | 0.92 | $221 | $303 |
| Texas | 0.93 | $223 | $306 |
| North Carolina | 0.94 | $226 | $309 |
| Georgia | 0.95 | $228 | $312 |
| Arizona | 1.01 | $242 | $332 |
| Florida | 1.02 | $245 | $335 |
| Pennsylvania | 1.03 | $247 | $339 |
| Illinois | 1.05 | $252 | $345 |
| Colorado | 1.08 | $259 | $355 |
| Washington | 1.15 | $276 | $378 |
| California | 1.32 | $317 | $434 |
| New York | 1.42 | $341 | $467 |
Index 1.00 is the national average. See construction cost by state for metro-level figures and the projects homeowners ask about most.
Where to buy materials
Links to suppliers are sponsored: if you buy through them, we may earn a commission at no extra cost to you. It never affects an estimate.
- Search The Home Depot“concrete mix 80 lb bag”
- Search Lowe's“concrete mix 80 lb bag”
Frequently asked questions
How many 80 lb bags of concrete make a cubic yard?
A cubic yard needs about 45 bags of 80 lb concrete mix. For anything larger than a small pad, ready-mix delivery is cheaper and far less work.
How thick should a concrete patio be?
Four inches is standard for patios, walkways and shed floors. Use 5–6 inches where vehicles will park, and add a compacted gravel base underneath.
How much does a 12 × 12 ft concrete slab cost?
A 12 × 12 ft slab at 4 inches thick takes about 1.8 cubic yards of concrete — roughly $240 to $330 delivered ready-mix, or about $340 to $460 if you mix it on site from 80 lb bags. Order 5 to 10% more to cover spillage and an uneven subgrade.
How long before I can walk on new concrete?
Foot traffic is usually fine after 24 to 48 hours, vehicles after about 7 days, and the slab reaches full design strength at 28 days. Concrete cures rather than dries, so keep it damp in hot weather to prevent surface cracking.
Does this cost change from state to state?
Yes. Applying each state's construction cost index to the national range of $240 to $329, the same job runs from about $221 to $303 in Ohio (index 0.92) to $341 to $467 in New York (index 1.42).
What is not included in this estimate?
Order 5–10% more than the calculated volume to cover spillage and uneven subgrade. The figure is a national planning average for the work described above, not a contractor's quote.
