Concrete Calculator · Manual
How to Use the Concrete Calculator
Choose the shape that matches the pour, enter measured dimensions with their units, set any extra allowance you want, and calculate one material-volume estimate.
Choose a pour type
Slab / patio / pad uses length, width, and thickness. Footing / trench uses length, width, and depth. Wall uses length, height, and thickness. Round column / post hole uses diameter and height/depth. Rectangular column uses width, depth, and height. Known volume starts from a volume you already have.
Enter units per dimension
Each linear dimension can use inches, feet, yards, millimeters, centimeters, or meters. You do not need to convert all measurements to the same unit first; the calculator normalizes them before applying the geometry formula. Known volume accepts ft³, yd³, m³, or liters.
Use Quantity for repeated identical pours
Quantity multiplies one calculated shape. For example, six identical round post holes use Quantity 6. If the pours are not identical, calculate them separately rather than averaging dimensions.
Set the extra / waste allowance
The calculator separates Net concrete volume from Concrete to order. The latter adds your selected allowance. The default is 10%, but 0%, 5%, 10%, 15%, and a custom value from 0% to 100% are available. The default is not a universal construction standard.
Read bag estimates
The reference table uses approximate yields of 0.30 ft³ for a 40 lb bag, 0.375 ft³ for 50 lb, 0.45 ft³ for 60 lb, and 0.60 ft³ for 80 lb. Bag counts use the adjusted order volume and always round up. If your product lists another yield, enter it as a custom ft³-per-bag or liters-per-bag value.
Copy, CSV, and Print / Save PDF
Copy result, Download CSV, and Print / Save PDF are enabled only after a valid calculation. All outputs use the same active result model. Editing any input makes the previous calculation stale, clears it, and disables those outputs until you calculate again.
Validation and scope
Required dimensions must be positive plain decimal numbers; Quantity must be a whole number from 1 to 1,000,000. Exponent notation, negative dimensions, zero dimensions, unsupported units, NaN, and Infinity are rejected. The app estimates material volume only; it does not design structural dimensions, check codes, calculate concrete strength, rebar, cost, or delivery logistics.