Concrete Slab Calculator
Volume, bags and weight for a rectangular slab — with waste allowance you control.
Slab dimensions
= 192" (16')
= 144" (12')
= 4"
Results update as you typeLive
Concrete Slab · Result
CalculatedORDER (INCL. 10% WASTE)
2.75 cubic yards to order, including 10 percent waste
- Net volume
- 2.37 yd³
- Waste
- 10%
- 80-lb bags
- 118
- 60-lb bags
- 157
Waste allowance 10%
SUGGESTED DEFAULTChangeOutput unit defaulted to cubic yards because at least one dimension was entered in imperial units
SUGGESTED DEFAULTReady-mix order increment 0.25 yd³ and minimum 1 yd³ are UI defaults; suppliers differ
SUGGESTED DEFAULTBag counts use each product's printed approximate yield; cubic-metre yields are derived from the printed cubic-feet figures — see Methodology
MFR SPECCode references & assumptions · 3
How this result is supported
- SUGGESTED DEFAULTOutput unit defaulted to cubic yards because at least one dimension was entered in imperial units
- ASSUMPTION
- SUGGESTED DEFAULTReady-mix order increment 0.25 yd³ and minimum 1 yd³ are UI defaults; suppliers differ
- ASSUMPTION
- MFR SPECBag counts use each product's printed approximate yield; cubic-metre yields are derived from the printed cubic-feet figures — see Methodology
- PRIMARY-VERIFIED
What do these evidence labels mean?
- PRIMARY-VERIFIED
- directly supported by one authoritative primary source, quoted with section/page/figure
- CROSS-VERIFIED
- independently supported by two or more appropriate authoritative sources
- DERIVED
- mathematically derived from PRIMARY-VERIFIED values; the derivation is preserved in data and in code
- INTERPRETED
- a source exists but translating it into calculator behaviour required interpretation
- CONVENTION
- recognised trade practice, not a mandatory provision
- ASSUMPTION
- product/design assumption or useful default with no authoritative basis
- UNVERIFIED
- insufficient authoritative evidence
Code references and product data are quoted in the units their source uses.
Reference checks are informational, not compliance determinations.
How concrete slab is calculated
Volume is deterministic geometry: length × width × thickness, converted to cubic yards. Waste covers spillage, uneven subgrade and the over-excavation every pour has, so the ordered figure is always the one to buy against.
Bag counts come from the yield printed on the product's own data sheet rather than a rounded rule of thumb, which is why the calculator names the product and the yield it used.
V = (length × width × thickness) ÷ 27
Volume in cubic yards, from dimensions in feet.
order = V × (1 + waste)
Waste covers spillage, uneven subgrade and over-excavation.