Slab 1
Length: — ft · Width: — ft · Thickness: — in
All-in-one concrete planner
Concrete Calculator
Calculate slabs, post holes, footings, walls, columns, bag counts, waste, and an order-ready quantity.
Project
Formula
Add each shape, then round once
Volume = measured area × concrete thickness, or the matching cylinder or prism for the other shapes. ConcreteQty converts the combined result to cubic yards, then applies waste and supplier rounding once to the total.
Common mistake
Averaging a slab with a footing
A 4-inch slab and an 8-inch footing do not share a thickness. Put them in separate sections. The planner adds the finished volumes and applies the allowance once, instead of hiding the extra concrete inside an average depth.
Worked quantities
Six different shapes, one ordering method
Each row is one section. The measured yardage, the order after 10% waste and 0.25 yd³ rounding, and the 80 lb bag count all come from the same engine as the form above.
| Job | Measured yd³ | Order yd³ | 80 lb bags |
|---|---|---|---|
| 12 × 10 ft slab, 4 in | 1.48 | 1.75 | 74 |
| 4 post holes, 12 in × 3 ft | 0.35 | 0.50 | 18 |
| 30 ft footing, 16 × 8 in | 0.99 | 1.25 | 49 |
| 20 × 8 ft wall, 8 in thick | 3.95 | 4.50 | 196 |
| 2 round columns, 12 in × 8 ft | 0.47 | 0.75 | 24 |
| 3 tubes, 12 in × 4 ft fill | 0.35 | 0.50 | 18 |
Field check
Split unlike sections
Keep sections separate when their thickness, shape, or units differ. The planner totals the finished concrete once, so a slab, footing, and post-hole run can share one purchasing result without averaging their dimensions.
Field check
Measure the concrete, not the work area
Use the final inside dimensions that concrete will occupy. Excavation, form lumber, gravel base, and overdig are different quantities and should not be folded into the concrete dimensions.
Field check
Recheck the order number
The calculated volume, waste allowance, and supplier rounding are shown separately. Confirm the final increment and minimum order with the supplier before treating the displayed order quantity as a purchase instruction.
Questions
What the all-in-one planner answers
Does the result include waste?
Yes. The default is 10%, and the calculated volume remains visible separately.
Can I combine several pours?
Yes. Add sections for slabs, footings, walls, post holes, or columns and ConcreteQty totals them.
Does this design the concrete structure?
No. It calculates quantity and purchasing estimates only.
Next step
Open the shape that matches this pour
Bag yields follow the cited manufacturer data. See sources and review dates.