TL;DR
For a 10' × 10' × 4" slab you need 1.24 cubic yards of concrete (add 10% waste → order 1.4 yards). At $175/yd delivered that's about $245 in material, before short-load fees. Use the concrete calculator to run your exact dimensions.
Why this trips people up
Concrete is priced by the cubic yard but sold in 60 lb and 80 lb bags at big-box stores, and in short-load vs full-load truck deliveries at ready-mix plants. Mix those units up and you're either $200 short at the pour or paying for a yard you don't need.
On a 20-yard slab we recently helped size, the crew almost ordered 22 yards "to be safe." Real answer after running the numbers: 21.2 yards with a 6% waste factor because the forms were tight and the finisher was experienced. Saved the homeowner ~$140.
What our data shows
Across recent MaterialCalc concrete jobs, 62% are 4-inch slabs on grade, median size 240 sq ft, and users default to a 10% waste factor. That matches ACI 301 guidance for well-formed flatwork.
The formula (and a worked example)
cubic yards = (length_ft × width_ft × thickness_in ÷ 12) ÷ 27
For a 12' × 14' × 4" patio:
- 12 × 14 × (4 ÷ 12) = 56 cu ft
- 56 ÷ 27 = 2.07 cu yd
- +10% waste = 2.28 cu yd → order 2.5 yards (plants round to quarter-yards)
Bags vs ready-mix vs short-load
| Volume needed | Best option | Why |
|---|---|---|
| < 0.5 yd (small footing, post base) | 60/80 lb bags | No delivery minimum, no waste |
| 0.5–1 yd | 80 lb bags (~45 bags) OR trailer mixer rental | Mixer beats hand-mixing 40+ bags |
| 1–3 yd | Short-load truck | Expect a $60–$150 short-load fee |
| 3+ yd | Standard ready-mix | Cheapest per yard; schedule finishers |
Bag yields (verify on the bag):
- Quikrete 60 lb → 0.45 cu ft
- Quikrete 80 lb → 0.60 cu ft
- Sakrete 5000 Plus 80 lb → 0.60 cu ft
Common mistakes
- Forgetting the thickness-to-feet conversion. 4 inches ≠ 4 feet. Divide by 12 first.
- Ordering exact yardage. Trucks measure by "load ticket." Always round up to the next quarter-yard.
- Ignoring the sub-base. A soft sub-base swallows concrete; compacted road base saves ~5% of your volume.
- Under-repping steel. For anything a vehicle drives on, run #3 rebar at 18" OC minimum (ACI 332 is the residential reference).
- Skipping the control-joint math. Cut joints at 2–3× slab thickness in feet (a 4" slab wants joints every 8–10 feet) or the slab tells you where they should have been.
Regional price notes (2026)
- Northeast: $190–$220/yd, higher on Long Island and NYC boroughs.
- South: $150–$180/yd, cheapest in TX and FL Panhandle.
- West: $180–$210/yd, add $20–$40 for high-strength (5000 psi) mixes common in seismic zones.
Ready to size your pour?
Run your exact numbers in the concrete calculator — it handles slabs, footings, columns and tubes and gives you both cubic yards and 60/80 lb bag counts.