Concrete Calculator
Slab volume is length times width times depth. A cylinder is π r² h. Cubic yards divide cubic feet by 27. Waste is 0 to 50 percent. This is an estimate, not structural design or code approval.
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How to estimate concrete volume
- Pick slab or cylinder. Slab uses length, width, and depth. Cylinder uses radius and height.
- Set each dimension unit. Depth often stays in inches while length stays in feet.
- Enter waste percent from 0 to 50. Optional: bag yield in cubic feet to ceil a bag count.
- Read ft³, yd³, and m³. Confirm mix and bags with a supplier. This is not code approval.
Concrete volume
Rectangular slab or right cylinder with optional waste
| Slab | L × W × D |
|---|---|
| Cylinder | π r² h |
| Cubic yard | 27 cubic feet |
| Waste factor | 1 + waste% / 100 |
| Bags | ceil(ft³ / bag yield) when yield is set |
| Advice | Estimate only. Not structural design or code approval. |
How slab and cylinder volumes are computed
Every length converts to feet. A slab is the product of those three edges. A cylinder is π times radius squared times height. Waste multiplies the volume. Cubic yards are cubic feet divided by 27. Bags round up when you type a yield.
Ready mix, bags, and waste
Ready-mix orders usually quote cubic yards. Bagged mix quotes a yield in cubic feet on the sack. Waste covers spillage and over-excavation, not a new mix design. Crushed stone coverage is the gravel calculator.
Estimate only, not structural design
This page does not size rebar, slump, psi, or frost depth. It does not approve a pour under a building code. A licensed engineer or the authority having jurisdiction owns those decisions. Floor area without thickness is square footage. Landscape depth is mulch.
Use cases
A patio slab, a sidewalk, or a round pier takeoff before you call a plant. Irregular edges and slope need extra geometry you type as bounding boxes.
Limits
Dimensions must be greater than 0. Waste stays from 0 to 50. Blank bag yield skips the bag row. CZNull does not receive the numbers.