Ready Mix Concrete Volume Calculator
Enter slab dimensions to estimate how much ready-mix concrete to order. Results include cubic feet, cubic yards, cubic meters, bag equivalents, and estimated cost.
Tip: For most residential slabs, a 4-inch thickness with 8%–12% waste is common.
How to use this ready mix concrete calculator
Ordering concrete is all about volume. This calculator helps you quickly convert project dimensions into a practical order amount for ready-mix delivery. You only need length, width, and depth. From there, the tool handles the math and adds a waste allowance so you can avoid coming up short during the pour.
The most common ordering unit in the U.S. is cubic yards. If you work with metric plans, we also provide cubic meters. For small jobs, bag equivalents are included to help compare ready-mix vs. bagged concrete.
Concrete volume formula (simple and reliable)
For rectangular areas like patios, floors, and pads, use:
- Volume (cubic feet) = Length (ft) × Width (ft) × Depth (ft)
- Depth (ft) = Depth (in) ÷ 12
- Cubic yards = Cubic feet ÷ 27
This page automates those conversions and includes a waste factor so your final recommendation is closer to what you should actually order.
Measuring common concrete projects
1) Slabs, driveways, patios, and garage floors
Measure maximum length and width in feet, then choose finished thickness in inches. If thickness changes across the slab, use the average thickness or divide the slab into sections and total the results.
2) Footings
Footings are usually long and narrow. Measure total linear footage, multiply by footing width and depth, and convert to cubic yards. For stepped footings, calculate each section separately and add them together.
3) Walls and stem walls
Use wall length × wall height × wall thickness. Convert thickness to feet first. Include pilasters or thicker sections as separate calculations so you do not underestimate.
4) Piers and columns (cylinders)
Cylindrical forms use a different formula:
- Volume = π × radius² × height
- Make sure radius and height are in the same unit before converting
For multiple piers, calculate one and multiply by quantity.
How much extra concrete should you order?
Most professionals include a waste factor because real jobs are not perfect. Subgrade variation, form movement, spillage, and over-excavation all increase demand.
- 5% waste: tightly controlled forms and simple pour geometry
- 8%–12% waste: typical residential slab projects
- 12%+ waste: uneven grades, complex forms, or first-time crews
If your supplier allows short-load adjustments or a follow-up mini-load, you can use a lower buffer. Otherwise, being slightly over is usually safer than stopping a pour.
Ready-mix vs bagged concrete
Bagged concrete can work for small pads, posts, and repairs. But once volume gets larger, ready-mix is usually faster, more consistent, and often cheaper per cubic yard when labor is included.
- 80 lb bags: about 0.6 cubic feet each
- 60 lb bags: about 0.45 cubic feet each
- 50 lb bags: about 0.375 cubic feet each
This calculator shows equivalent bag counts so you can compare options before ordering.
Before you place your concrete order
Confirm these details with your supplier:
- Required compressive strength (e.g., 3000 PSI, 4000 PSI)
- Maximum aggregate size
- Slump target and workability needs
- Air entrainment (important in freeze-thaw climates)
- Fiber reinforcement or additives, if needed
- Truck access and chute reach at the site
- Minimum load and short-load fees
Quick FAQ
Should I order exactly what the math gives me?
No. Include a waste factor. Exact math rarely matches field conditions perfectly.
What if my depth is not uniform?
Split the area into smaller rectangles, calculate each section, and add totals. This gives a more accurate estimate.
How are ready-mix trucks sized?
Many full-size mixers carry around 9–10 cubic yards, but capacities vary by region and legal load limits.
Final takeaway
A ready mix concrete calculator helps you estimate quickly and order confidently. Start with accurate measurements, use a realistic waste factor, and confirm mix specs with your supplier before pour day. Good prep is the easiest way to save time, reduce rework, and get better concrete results.