Concrete & Masonry
Concrete Volume Calculator
Enter the dimensions of your pour — rectangular or cylindrical — in feet and inches to get the cubic yards of ready-mix to order, with wastage and an optional cost estimate.
Formula tested · Local units · No sign-up
Project inputs
Enter measurements
Use your preferred units. Results update automatically.
Show the calculation methodFormula, conversions, rounding, and assumptions+
Rectangular pours (slabs, footings, walls) use volume = length × width × depth. Cylindrical pours (columns, post holes, sonotube piers) use volume = π × (diameter ÷ 2)² × depth. Either result is multiplied by the number of identical pours.
Because depth is usually measured in inches while plan dimensions are in feet, the calculator converts everything to a common unit before multiplying — 6 inches is 0.5 ft, not 6.
US ready-mix is sold by the cubic yard (27 cubic feet), so the total is divided by 27 and rounded up to the next quarter yard, which is how most plants take orders.
Real-world example
Worked example: 10 ft × 10 ft pad, 6 in thick
- Convert depth: 6 in ÷ 12 = 0.5 ft.
- Volume: 10 × 10 × 0.5 = 50 cubic feet.
- Convert to yards: 50 ÷ 27 = 1.85 cubic yards.
- Add 10% wastage: 1.85 × 1.10 = 2.04 cubic yards.
- Round up to the ordering increment: 2.25 cubic yards.
Order 2.25 cubic yards. At an example price of $150 per yard with 8% sales tax, that's $337.50 + $27.00 = $364.50.
Before you start
How to measure
- For rectangular pours, measure length and width at the top of the forms in feet, and depth in inches at several points — use the largest reading.
- For cylindrical pours, measure the inside diameter of the form or hole (a 12-inch sonotube is 12 inches inside) and the depth from bottom to finished level.
- For multiple identical piers or post holes, calculate one and use the 'number of pours' field instead of adding by hand.
Local guidance
Notes for United States
- US ready-mix plants order in cubic yards and usually have a minimum load, with a short-load fee for small deliveries — for a handful of post holes, bagged concrete may be more practical.
- Footing and pier depths are governed by local frost depth and code — check with your building department before digging.
- Sales tax varies by state and locality and is entered manually; supplier quotes usually exclude it.
Quick reference
Volume formulas by pour shape
| Shape | Formula | Typical use |
|---|---|---|
| Rectangular | length × width × depth | Slabs, footings, walls |
| Cylindrical | π × (diameter ÷ 2)² × depth | Columns, piers, post holes |
Planning formulas only — thickened edges, keyways and bell-outs add volume beyond these shapes.
Good to know
Common mistakes to avoid
- Multiplying feet by inches without converting — this overstates volume by 12×.
- Using the full diameter instead of the radius in the cylinder formula, which quadruples the volume.
- Ordering the exact calculated volume with no wastage: over-excavated holes and spillage almost always consume 5–10% extra.
- Forgetting that concrete around a fence post displaces less than the full hole — this calculator assumes the full cylinder, which is the safe (slightly generous) assumption.
Need help?
Frequently asked questions
How much concrete for 12 post holes, 12 inches in diameter and 3 feet deep?
Each hole is π × 0.5² × 3 = 2.36 cubic feet. Twelve holes = 28.3 cubic feet = 1.05 cubic yards. With 10% wastage that's 1.15, so order 1.25 cubic yards — or about 52 80 lb bags (0.6 cubic feet each) if you'd rather mix by hand.
How many 80 lb bags equal one cubic yard?
An 80 lb bag yields about 0.6 cubic feet, so one cubic yard (27 cubic feet) is roughly 45 bags. Above about a yard, ready-mix delivery is usually more practical than bagged mix.
How is this different from the concrete slab calculator?
The slab calculator is a streamlined version for flat rectangular slabs only. This one also handles cylindrical pours (piers, columns, post holes) and multiple identical pours in one calculation.
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About this calculator
- Written by:
- BuildMeasure Editorial Team
- Technically reviewed by:
- Pending independent technical reviewer (formula unit-tested; see methodology)
- Last reviewed:
- 2026-07-16
- Formula version:
- 1.0.0
- Region reviewed for:
- United States
- Spotted an error?
- Report a correction
Methodology
- Rectangular pours use volume = length × width × depth × count; cylindrical pours use volume = π × (diameter ÷ 2)² × depth × count. All inputs are converted to SI units (metres) before any arithmetic to avoid unit drift.
- The wastage allowance is applied to the exact volume, then the total is rounded UP to the next 0.25 of the regional ordering unit (cubic yards in the US, cubic metres elsewhere), because ready-mix suppliers typically sell in quarter-unit increments.
- The cost estimate simply multiplies the suggested order quantity by the price you enter, then applies the tax rate you enter. No prices are built in.
- The formula is covered by automated unit tests, including hand-calculated worked examples, and is versioned (see formula version on this page).
Sources & standards
- Unit definitions: 1 ft = 0.3048 m and 1 yd³ = 0.764554857984 m³ (exact international definitions).
- Ordering increments: Quarter-yard ordering is standard US ready-mix practice; confirm with your plant.
This tool provides a material estimate for planning purposes only. It is not a quotation, and it does not size reinforcement, check ground conditions, or replace professional structural advice. Confirm quantities and mix specification with your supplier before ordering.