Quick answer
Concrete Calculator: what it calculates
Concrete Calculator calculates concrete volume from length, width and depth. The core method is Cubic yards = length x width x depth in feet / 27.
Everyday Calculators
Concrete Calculator
Use this concrete calculator for slabs, patios, footings, and pads by entering length, width, depth, waste, and price per cubic yard.
Reviewed May 25, 2026EstimateFormula shown
ResultConcrete volume
InputsLength, Width, Depth, Waste percent, Price per cubic yard
FormulaConcrete volume formula
Live calculator
Concrete
Concrete to order1.63 yd³
Includes 10% extra for waste and uneven forms.
80 lb bags74
Approximate bag count using about 0.6 cubic feet per 80 lb bag.
Estimated concrete cost$260.74
Concrete yards multiplied by the entered price per yard.
Volume breakdown
Concrete is usually ordered in cubic yards.
| Measure | Amount |
|---|---|
| Cubic feet | 40 ft³ |
| Base cubic yards | 1.48 yd³ |
| Order amount | 1.63 yd³ |
Formula
Concrete volume formula
Cubic yards = length x width x depth in feet / 27Depth entered in inches is converted to feet before calculating volume.
How to use
Steps
- Enter the concrete area's length and width in feet.
- Enter the slab or form depth in inches.
- Add waste percent for uneven forms, spillage, and ordering buffer.
- Review cubic yards, bag estimate, and material cost.
Example
Sample calculation
12 ft x 10 ft x 4 in1.48 yd³ before waste
With 10% waste1.63 yd³
80 lb bagsAbout 74
Calculator use
Best for
- Quick concrete volume from length, width and depth.
- Quick everyday math with the result and formula in one place.
- Shopping, date, time, unit, school, or household comparisons.
- A fast check before moving the numbers into a spreadsheet.
Before relying on it
Check first
- Entering length, width and depth from different time periods or scenarios.
- Mixing units, dates, or original values across the same calculation.
- Rounding early and then using the rounded number in another step.
- Copying a result without checking whether the inputs match the real-world question.
Benchmarks
How to read the result
The calculator is a decision aid, not a fixed rule. Use the output to compare scenarios and document your assumptions.
2 inLight overlay
Usually too thin for structural slabs unless specified by a pro.
4 inCommon slab
Often used for patios and walkways, depending on soil and load.
6 in+Heavier use
Often considered for driveways, pads, or heavier loads.
Calculator accuracy
Methodology and assumptions
The formula, inputs, example, and limitations are shown so the result is checkable, not just a number in a box.
Formula
Cubic yards = length x width x depth in feet / 27
Inputs used
Length, Width, Depth, Waste percent, Price per cubic yard
Limitations
Results are estimates for quick planning and should be checked before important financial, legal, tax, health, or business decisions.
Last reviewed
May 25, 2026
Cite this page
Toolkit Shelf. Concrete Calculator. Retrieved May 25, 2026, from https://toolkitshelf.com/tools/concrete-calculator
FAQ
Common questions
How do I calculate concrete yards?
Multiply length by width by depth in feet to get cubic feet, then divide by 27 to convert to cubic yards.
How many 80 lb bags are in a cubic yard?
An 80 lb bag often yields about 0.6 cubic feet, so one cubic yard takes about 45 bags.
Should I add extra concrete?
Many projects add 5% to 10% extra for waste, uneven subgrade, and measurement differences.