Concrete calculator: how much do you need?
Enter your dimensions to estimate concrete volume in cubic yards, with a separate planning allowance.
Choose a shape, then enter your dimensions. Prefilled values are examples, not recommended construction dimensions. Results update as you type.
Slab / Footing / Wall
Rectangular slabs, patios, footings, and walls
View result ↓Where should I measure?
Example concrete volume
1.23 cubic yards
Calculated from the example dimensions, before allowance.
1.36 cubic yards with 10% allowance
A planning scenario, not a final order quantity. Confirm the allowance with your supplier.
Equivalent base volume: 33.33 cubic feet.
Bag quantities and approximate weight
- Bags including 10% allowance
- 82 × 60-lb bags or 62 × 80-lb bags.
- Weight without allowance
- 5,000 lb (2.5 US short tons), using an assumed 150 lb per cubic foot.
Bag counts use QUIKRETE Concrete Mix No. 1101 yields; other products differ. Weight is a separate general estimate, not the bagged product weight.
Your dimensions and estimate carry into the request. Choose the project type next. Matching depends on local availability.
How do you use the concrete calculator?
To use the concrete calculator, choose the shape of your pour, enter each measurement with its unit, and read the calculated volume. Use the diagram to identify the measurements. Quantity repeats identical shapes; calculate different sizes separately.
Use the thickness or dimensions in your project scope. The example values do not specify the correct design for your project. Copy or download the result to discuss with a supplier, or carry it into a contractor request.
How are the results calculated?
The calculator converts measurements to feet, calculates the shape volume, and divides cubic feet by 27 to get cubic yards. Displayed volumes are rounded to two decimal places; allowance and bag calculations use the unrounded volume.
- Rectangular slab, footing, or wall
- Length × width × thickness or height × quantity.
- Column or round footing
- π × (diameter ÷ 2)² × height × quantity.
- Circular slab or hollow tube
- π × [(outer diameter ÷ 2)² − (inner diameter ÷ 2)²] × height × quantity. Use an inner diameter of zero for a solid circle.
- Curb and gutter
- [Gutter width × flag thickness + curb depth × (curb height + flag thickness)] × length × quantity. Gutter width excludes the curb; curb height is measured above the gutter surface.
- Solid-filled stairs
- Width × rise × [run × n × (n + 1) ÷ 2 + platform depth × n], where n is the number of steps. The platform extends beyond the last tread and is filled to the full total stair height. This formula does not model a thin stair slab over a sloping base.
Which assumptions affect the estimate?
- Planning allowance: The second volume adds 10%. This is a fixed scenario for planning, not a universal ordering recommendation. Confirm the allowance for the forms, subgrade, placement method, and job conditions.
- Bag quantities: The tool uses approximate yields of 0.45 cubic feet per 60-lb bag and 0.60 cubic feet per 80-lb bag from QUIKRETE Concrete Mix No. 1101 product data (revised October 2022; checked September 23, 2026). Bag counts include the 10% allowance and round up to whole bags. Check your chosen product because yields differ.
- Weight: Base volume × an assumed 150 lb per cubic foot, without the allowance. The ACI Concrete Terminology (2013) describes normalweight concrete at approximately this density. Actual mix density varies; confirm it with your supplier. This estimate is not a transport or load-capacity assessment. One US short ton equals 2,000 lb.
- Scope: The result covers the entered geometry. It does not automatically add thickened edges, separate footings, irregular excavation, or other unentered sections. Ready-mix prices, delivery minimums, pumping, and installation costs are not calculated.
What should you confirm before ordering?
Confirm the dimensions, concrete mix, final order quantity, and allowance with your supplier or contractor. Ask about delivery minimums and placement requirements. A volume estimate helps describe the job; it does not establish structural design or the correct thickness.