Free contractor tool
Concrete Calculator
Enter length, width and thickness to see the cubic yards a pour takes. Add a section for an L-shape, an apron or a thickened strip, choose your own waste allowance, and get the quantity you would actually order.
Pour dimensions
The fields start with example dimensions so you can see the math. Replace them with your own — they are a starting point, not a recommendation.
Area
Your number, not ours. RHACOVA does not publish a standard allowance because the honest answer depends on your subgrade, forms and crew.
The step your supplier actually sells in. 0.25 is only a starting value.
Your result
Quantity decision
Order volume
Same volume in cubic feet
Why this number?
cubicInches = Σ (count * lengthIn * widthIn * thicknessIn); cubicYards = cubicInches / 46656; adjusted = cubicYards * (1 + waste); order = ceilToIncrement(adjusted)
Inputs
- section1Length
- 240.00 in
- section1Width
- 120.00 in
- section1Thickness
- 4.00 in
- section1Count
- 1
- Waste allowance
- 10.00%
- Order increment
- 0.2500 cu yd
Results
- Theoretical volume (cu ft)
- 66.67 cu ft
- Theoretical volume (cu yd)
- 2.4691 cu yd
- Waste allowance volume
- 0.2469 cu yd
- Waste-adjusted volume
- 2.7160 cu yd
- Order quantity
- 2.7500 cu yd
Formula concrete.rectangularSections · engine shared.concrete@1.1.0 · rectangular-volume · rounding half-even to 6 decimals.
A quantity is not a bid
Cubic yards tell you what to order. What you charge still depends on material cost, loaded labor, equipment, overhead and the margin you need. RHACOVA carries this quantity into the job bid so you price it instead of guessing.
Price this pour: build the job bidStill no account, and nothing you type leaves your device. Signing in only comes up if you choose to save the bid as an estimate.
How concrete volume is calculated
Concrete for any rectangular pour is a volume: length × width × thickness. The only trick is units. Thickness is usually in inches while length and width are in feet, so every dimension is converted to the same unit before multiplying. This calculator converts all three to inches, multiplies them into cubic inches, then divides by 1,728 for cubic feet and by 27 for cubic yards. Concrete is sold in cubic yards in the US, so that is the primary result, with cubic feet shown alongside it.
A pour that is not one rectangle is still made of rectangles. Add a section for the apron, the L, the thickened strip or the second pad, and the sections are summed before the waste allowance is applied. The “how many” field repeats an identical section.
Base volume vs waste-adjusted volume vs order quantity
Base volume is pure geometry: what the forms hold if the subgrade is flat and nothing is spilled.
Waste-adjusted volume is the base volume multiplied by the allowance you enter. Real pours lose material to uneven subgrade, over-excavation, spillage and concrete left in the truck. The right allowance depends on your site, your crew and your subgrade — RHACOVA does not publish an “industry standard” figure, because the honest answer is that it varies. Enter the number your own jobs justify; enter 0 and the two figures are identical.
Order quantity is the waste-adjusted volume rounded up to the increment your supplier sells in. Rounding is always upward: ordering short means a cold joint or a second truck.
The formulas and the units
- Cubic inches = length (in) × width (in) × thickness (in) × how many
- Cubic feet = cubic inches ÷ 1,728
- Cubic yards = cubic inches ÷ 46,656, equivalently cubic feet ÷ 27
- Waste-adjusted volume = base volume × (1 + waste percentage)
- Order quantity = waste-adjusted volume rounded up to the order increment
Conversions are exact and happen in one shared unit system, not per page. Results are kept at full precision internally and rounded only for display, so the number you read is never a rounded number that was rounded again.
What this calculator does not do
This is a quantity tool. It does not size a slab, recommend a thickness, specify a mix or strength, design reinforcement or price material and labor. Those depend on loads, soils, local code and your own costs — check them against the drawings, your supplier and your engineer.
Worked example
A 20 ft × 10 ft pour at 4 in thick, with a 10% waste allowance, ordered in 0.25 cu yd increments:
- Base volume: 66.67 cu ft
- Base volume: 2.4691 cu yd
- Waste allowance: 0.2469 cu yd
- Waste-adjusted volume: 2.7160 cu yd
- Order quantity: 2.75 cu yd
The example is computed by the same engine as the calculator above, so it always matches the tool.
Common calculation mistakes
- Mixing units: thickness in inches multiplied by feet gives a number 12× too small.
- Dividing cubic feet by 3 instead of 27. A cubic yard is 3 × 3 × 3 feet, not 3 feet.
- Ordering the base volume. Subgrade, spillage and material left in the truck are real — decide your own allowance instead of copying one.
- Rounding down to the increment. Short concrete means a cold joint or a second truck.
- Measuring the forms instead of the excavation. If the subgrade dips, the slab holds more than the drawing says.
- Treating one rectangle as the whole pour. Break L-shapes, thickened edges and footings out as separate sections.
Other concrete quantities
- Concrete Slab Calculator
How much concrete does one rectangular slab take?
- Concrete Driveway Calculator
How much concrete does a driveway of this size take?
- Concrete Footing Calculator
How much concrete do these footings or pads take?
- Rebar Calculator
How many bars and linear feet does this grid take?
- All RHACOVA calculators
Once the quantity is settled, the next questions are cost, price and profit.
After the quantity: cost, price, profit
- True Job Cost Calculator
A quantity is not a cost. Add material, loaded labor, equipment, disposal and the rest to see what the pour actually costs you.
- Markup & Margin Calculator
Turn that cost into a price, and see the margin the price actually leaves.
Learn the method
- How to Estimate Concrete Cost: Yards, Waste, Job Cost and Price
Estimate the cost and selling price of a concrete job from quantity, contractor-entered prices and job costs.
- What Is True Job Cost?
Know which costs belong in a construction job cost and how to total them.
- Construction Pricing: Cost vs Price vs Profit
Understand the difference between cost, price and profit before pricing construction work.
From concrete quantity to a complete job
See how the same quantity continues through cost, pricing, Profit Guard, a standard Estimate and the job-costing loop in RHACOVA concrete estimating software.