Volume formula
length (ft) × width (ft) × thickness (in) ÷ 12 ÷ 27 = yd³
Example: 12 × 12 × 4 ÷ 12 ÷ 27 = 1.78 yd³ net.
Concrete planning estimate
Concrete Patio Calculator
Estimate concrete volume, bag count, gravel base, wire mesh, and rough material cost for a concrete patio slab. The patio preset uses 4 in thickness, 4 in gravel base, wire mesh reinforcement, and a 5% waste factor.
What this patio calculator estimates
The patio preset applies standard residential patio defaults: 4 in slab thickness, 4 in compacted gravel base, wire mesh reinforcement, and 3000 psi (M250) concrete. Adjust any input for your specific project.
- Concrete volume in cubic yards or cubic meters.
- 40 lb, 60 lb, and 80 lb bag counts for imperial estimates.
- Ready-mix recommendation when volume exceeds 1 yd³.
- Compacted gravel base volume and approximate weight.
- Form board count from patio perimeter.
- Wire mesh planning area (10 ft × 10 ft sheets with overlap).
- Rough material cost range for concrete, gravel, forms, and mesh.
Patio concrete formula
Patio estimates use the standard slab formula with patio-appropriate defaults.
Patio waste factor
Use 5% for patios with straight square edges and accurate forms. Increase to 8–10% for irregular shapes or uncertain subgrade.
Bags vs. ready-mix
Patios up to about 1 yd³ can use bags. Above 1 yd³, ready-mix is practical and usually less expensive per yard. Most 12 × 12 patios are at this boundary.
Common patio size estimates
Pre-calculated for 4 in thickness, M250 concrete, 5% waste, and 4 in gravel base.
| Patio size | Net yd³ | Ordered yd³ | 80 lb bags | Ordering |
|---|---|---|---|---|
| 10 × 10 × 4 in | 1.23 | 1.30 | 59 | Bags or ready-mix |
| 12 × 12 × 4 in | 1.78 | 1.87 | 85 | Ready-mix recommended |
| 14 × 14 × 4 in | 2.42 | 2.54 | 116 | Ready-mix recommended |
| 16 × 20 × 4 in | 3.95 | 4.15 | 189 | Ready-mix recommended |
| 20 × 24 × 4 in | 5.93 | 6.22 | 283 | Ready-mix required |
Patio ordering checklist
Check these items before placing your concrete order or heading to the home center.
- 3000 psi (M250) concrete, or 4000 psi in cold climates.
- Compacted gravel base at 4 in minimum depth.
- Wire mesh (welded wire fabric) for crack control, supported at mid-depth.
- Form boards sized to slab thickness, secured with stakes.
- Control joints every 8–10 ft (match 24× thickness rule).
- Not included: labor, delivery, permits, finishing tools, curing compound, or sealer.
Concrete patio calculator FAQ
How much concrete does a 12×12 patio need?
A 12 ft × 12 ft × 4 in patio slab needs about 1.78 yd³ before waste and about 1.87 yd³ with 5% waste — roughly 85 bags of 80 lb concrete.
How thick should a concrete patio be?
Most residential concrete patios are 4 in thick. Patios that will have heavy planters, spas, or vehicle access should be 5–6 in. Check your local code.
Do I need rebar in a patio slab?
Wire mesh is the common choice for residential patios. Rebar adds extra crack resistance for larger slabs or areas with unstable soil. Place reinforcement at mid-depth on chairs or dobies.
Do I need a permit for a concrete patio?
Permit requirements vary by location and patio size. Many municipalities allow small detached slabs without a permit, but attached slabs, drainage considerations, or large area thresholds may trigger permit requirements. Check with your local building department.
How many bags of concrete for a 10×10 patio?
A 10 × 10 × 4 in patio needs about 1.30 yd³ with 5% waste — roughly 59 bags of 80 lb concrete. This is at the boundary where renting a mixer makes sense.
What concrete PSI should I use for a patio?
3000 psi (M250) is the standard for residential patios. In freeze-thaw climates, 4000 psi (M300) with air entrainment reduces surface scaling from deicing salts.
Related concrete calculators
Planning estimates only
These are rough material estimates for planning purposes. They are not purchasing guarantees, engineering designs, or code compliance guidance. Verify slab thickness, subbase, reinforcement, drainage, control joints, and local permit requirements before starting work.