← All construction calculators
Concrete slab calculator (cubic yards)
Exact geometric volume of a rectangular slab in cubic yards — the unit ready-mix is ordered in.
Loading calculators…
How it’s computed
Volume = length (ft) × width (ft) × (thickness in ÷ 12) ÷ 27, quantized to 0.01 cy. Dividing cubic feet by 27 is the standard yards conversion.
Decimal-exact and deterministic: identical inputs always return identical results. This is the same math Ask Donnie’s estimating engine runs — not an approximation, and never a language model doing arithmetic.
Common questions
Why cubic yards?
Ready-mix concrete is sold by the cubic yard. This gives you the exact geometric volume of the slab.
Should I order extra?
This calculator returns exact geometry with no waste factor. If you want a takeoff that includes a waste allowance plus aggregate base and rebar, use the slab takeoff calculator — it applies 10% waste by default.
Related calculators
Need the whole estimate, not just this number?
Ask Donnie turns a description or a plan into a full itemized estimate — deterministic math, real cited pricing, an AACE accuracy class. Free to start, watermarked deliverables included.