calcanvil

Patio Concrete Calculator

12 ft12 ft4″depth
✓
✓
✓

Order 1.85-1.96 yd³

Plan volume 1.78 yd³ (48 ft³); range = NRMCA CIP-8 4-10% ordering allowance.

  • Volume is plan geometry; NRMCA CIP 8 says order 4-10% over plan (subgrade, forms, spillage).
  • A 1/8" thickness variation on a 4" slab is a ±3% volume swing; measure thickness honestly.
  • Ready-mix increments and short-load fees are vendor practice; confirm with your plant.

Why This One Is Different

A backyard patio is usually the smallest pour on this whole site, which is exactly why it's easy to under-order and end up paying a short-load fee at the ready-mix plant. Twelve feet by twelve feet at a standard 4-inch thickness works out to 144 square feet and just under 2 cubic yards of plan volume; add the usual ordering allowance and you land closer to 2.1 to 2.2 yards. This calculator runs that math against your actual dimensions, not the 12×12 default, and reminds you where control joints typically go so a decorative slab doesn't crack in a random, ugly line.

Where the Numbers Come From

  • Even a small patio starts from the same volume formula as any slab: plan volume is length × width × (thickness ÷ 12) ÷ 27, which for a 12×12 ft patio at 4 inches works out to 1.78 cubic yards before any ordering allowance. Source: worked example, closed-form geometry
  • Order more than your plan volume, even on a small pour: NRMCA guidance is to order 4-10% more than plan-derived volume, since form deflection, subgrade irregularity, spillage, and settlement mean placed volume never equals plan volume, and a small patio pour is not exempt. Source: NRMCA, CIP 8: Discrepancies in Yield (2021 reprint)
  • Ready-mix plants commonly charge a short-load fee below a minimum truck volume (often around 3-4 cubic yards), a vendor practice, not an NRMCA standard, that makes small pours worth ordering slightly generous. Source: trade convention, labeled as such (not codified in a standard)

More Questions

Can I pour a patio slab myself?

A small patio is within reach for an experienced DIYer with help on placement day, but concrete sets fast once the truck arrives. Have your forms, base, and reinforcement fully ready, and enough hands, before the pour starts.

Related Calculators

Formulas, waste factors, and cost models on this page follow the sourced conventions on our methodology page. Estimates only; verify with your supplier and local code.