Concrete for a 20×30 Slab at 4" Thick
A 20 ft × 30 ft slab poured 4 inches thick is 600 sq ft and needs 7.41 cubic yards of concrete — order 8.00 CY to cover 8% waste, or about 360 80-lb bags for a small pour. Adjust the dimensions below for your project.
Doing this for work? Estimate the whole job in minutes.
JRIQ turns plans and site photos into full material + labor estimates with AI — built by the team behind these calculators.
Try it free →
Want the full guide — tools, step-by-step, common mistakes and FAQ? See the Concrete Slab Calculator.