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 volume is expressed in cubic yards (27 cubic feet). Supplier rounding is optional and uses only the cubic-yard increment entered from the current quote.
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.
- For this worked example, enter the supplier's stated 0.25 yd³ increment: 2.04 yd³ rounds up to 2.25 yd³.
The example becomes 2.25 yd³ only with the explicitly entered 0.25 yd³ quote increment. Replace it with the actual supplier term and use the related quote calculator for minimums, delivery, fees and tax.
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 is ordered in cubic yards. Minimums and short-load fees are supplier-specific commercial terms; copy them into the related ready-mix cost calculator.
- 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.
- Leaving allowance at zero without checking over-excavation, form variation, displacement and placement losses for this specific pour.
- 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.
Keep planning
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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:
- 2026-07-23
- Formula version:
- 1.1.0
- 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 chosen allowance is applied to the exact volume. Supplier rounding occurs only when you enter the increment shown on the current quote; if that field is blank, the planning volume remains unrounded.
- The preliminary material cost multiplies the planning or supplier-rounded quantity by the price you enter. Tax is added only after you confirm that the entered price excludes tax and supply a rate; an unresolved basis produces a subtotal, not a final total.
- 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).
- Supplier order terms: Order increment, physical minimum, billed minimum and short-load charges must be copied from the current supplier quote.
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.