How Much Concrete for a Patio?

By RugCalc Editorial Team · Last updated: 2026-10-13 · 7 min read

Quick answer: cubic yards = area × thickness (ft) ÷ 27. A 12×12 patio at 4 in needs ~1.8 cu yd; a 20×20 patio needs ~5 cu yd. Here's the full method.

Thickness first

A residential concrete patio is typically 4 inches thick on a compacted base. Go to 5–6 in if it carries heavy loads like a hot tub or is intended for vehicles. Thickness drives volume, so settle it before you calculate — changing it later changes the yardage a lot.

Cubic yards by size

Patio size	Sq ft	4 in (cu yd)	6 in (cu yd)
10×10	100	1.2	1.9
12×12	144	1.8	2.7
16×20	320	4.0	5.9
20×20	400	4.9	7.4

Ready-mix is ordered in full cubic yards, so round up to the next whole yard after the math.

Cost estimate

A concrete patio runs about $6–$10 per sq ft installed. A 12×12 slab is roughly $1,000–$1,500 once site prep, forms, reinforcement, and finish are included. The concrete material itself is a smaller share than labor and prep — get a local quote rather than trusting one national number.

Worked example

A 12×12 patio at 4 in:

• Area = 144 sq ft; volume = 144 × 0.333 ÷ 27 = 1.78 cu yd → order 2 cu yd
• Material ≈ 2 × $140 ≈ $280
• Base, forms, labor ≈ $800–$1,200
• Total ≈ $1,000–$1,500

Matches the $6–$10 per sq ft range for 144 sq ft.

The base below

Concrete needs a stable base: typically 3–4 in of compacted gravel on firm soil. Skimping on the base is how patios crack and settle. Excavate, add the gravel, compact it, then form and pour — the base is the part you can't see but that decides how long the slab lasts.

Common mistakes

• Ordering short on thickness. 4 in is the floor, not the ceiling.
• No gravel base. Pouring on bare dirt = settling cracks.
• Quoting material only. Prep and labor usually cost more than the concrete.
• Forgetting to round up. Ready-mix comes in whole yards.

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