Calculators
Concrete Slab Calculator
Circular slabs use diameter and thickness instead of length and width. Preset: 12 ft diameter, 4 inches thick, 10% waste.
The table shows bag count and ready-mix cubic yards side by side. Check the yield on your bag label — 60 lb and 80 lb bags differ.
Controls below switch between rectangle and circle shapes.
| Item | Area | Size | Buy |
|---|---|---|---|
| Concrete | — | 41.5 cu ft | 93 bags |
| Ready-mix equivalent | — | 1.5 cu yd | 2 cubic yards |
Assumptions
- Circular slab: 12 ft diameter × 4 in
- Waste factor: 10%
- Volume: 37.70 cu ft
- Volume with waste: 41.47 cu ft (1.54 cu yd)
- Bag yield: 0.45 cu ft per bag (check bag label)
- Above about 1 cubic yard, ready-mix delivery is often more practical than bags — compare options locally.
- Estimates only. Check the coverage figure on your product before buying.
Supplies checklist
- Gravel or crushed stone base
- Wire mesh or rebar (slabs)
- Form boards and stakes
- Concrete mixer or mixing tub
- Float and edger
Estimates only. Check the coverage figure on your product before buying.
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