Patio volume
length × width × thickness = measured volumeIf a patio has separate rectangles, calculate each size independently or use the identical-sections field only for matching areas. Apply waste after combining the sections.
Concrete patio calculator
Estimate the concrete needed for a rectangular patio, including a configurable allowance for irregular excavation and placement loss.
Enter project dimensions
Use the finished dimensions inside your forms.
Use the formed dimensions after drainage is resolved
A patio normally needs positive drainage away from buildings, so the prepared base and form elevations matter as much as plan dimensions. The calculator assumes uniform thickness and does not model a sloped top over an uneven base.
- Separate steps, thickened edges, piers, and irregular extensions.
- Confirm joints, reinforcement, finish, strength, access, and curing.
- Recheck depth at several locations before ordering concrete.
Measure inside the forms
Measure the planned finished footprint at the form faces. Check excavation depth at several points; a low area can consume more concrete than a single center measurement suggests. Do not count the gravel subbase as concrete thickness.
Worked example
16 ft × 12 ft patio at 4 in thick
Measured16 × 12 × (4 ÷ 12) = 64.00 ft³
With 10% waste64.00 × 1.10 = 70.40 ft³
Ready-mix70.40 ÷ 27 = 2.61 yd³
80 lb bags70.40 ÷ 0.60 = 117.34, rounded up to 118
Patio-specific assumptions
- The patio is level and has uniform thickness.
- Steps, thickened edges, grade beams, and curved borders are not included unless calculated separately.
- Slope for drainage changes elevation, but a uniformly thick sloped slab still uses the same volume formula.
Plan beyond the volume
Verify subbase, drainage slope, reinforcement, control-joint spacing, surface finish, weather, curing, and access before the pour. Concrete quantity alone does not establish a safe or durable patio design.