Formula
Concrete volume formula
Concrete volume = length x width x depth after converting all dimensions to one base unitFeet mode uses inches and cubic yards; meters mode uses centimeters and cubic meters.
Concrete Calculator
Use this concrete calculator for slabs, patios, footings, and pads by entering length, width, depth, waste, and price per cubic yard or cubic meter.
Live calculator
Concrete
Concrete to order1.63 yd³
Includes 10% extra; 1.63 yd³ / 1.25 m³.
80 lb bags74
Approximate bag count using about 0.6 cubic feet per 80 lb bag.
Estimated concrete cost$260.74
yd³ multiplied by price per cubic yard.
Volume breakdown
Concrete is usually ordered in cubic yards.
| Measure | Amount |
|---|---|
| Cubic feet | 40 ft³ |
| Base cubic yards | 1.48 yd³ |
| Base cubic meters | 1.13 m³ |
| Order amount | 1.63 yd³ / 1.25 m³ |
Material estimates need field measurements and a waste allowance. Supplier coverage, cuts, breakage, compaction, and local installation requirements can change the order quantity.
How to use
Steps
- Choose feet or meters for the project measurements.
- Enter the concrete area's length, width, and depth.
- Add waste percent for uneven forms, spillage, and ordering buffer.
- Review cubic yards, cubic meters, bag estimate, and material cost.
Example
Sample calculation
12 ft x 10 ft x 4 in1.48 yd³ before waste
Metric equivalent3.66 m x 3.05 m x 10.16 cm
With 10% waste1.63 yd³ / 1.25 m³
80 lb bagsAbout 74
Calculator use
Best for
- Estimating cubic yards for slabs, patios, footings, pads, walkways, and small pours.
- Checking ready-mix volume before calling a supplier or comparing bagged concrete.
- Estimating 80 lb bags for small jobs where a truck delivery would be too much.
- Adding waste for uneven forms, spillage, over-excavation, and field adjustments.
Before relying on it
Check first
- Using inches, feet, and yards inconsistently across length, width, and depth.
- Ordering exactly the calculated volume with no waste allowance for real jobsite conditions.
- Using the result for structural design, load-bearing engineering, permits, or code compliance.
- Forgetting that bag yield, slump, reinforcement, subbase, and form accuracy can change the real quantity.
Details
What to know before using the result
Unit mathKeep dimensions aligned
The calculator supports feet/inches or meters/centimeters and converts both systems to the same volume base before estimating.
Cubic yards27 cubic feet per yard
Concrete is commonly ordered by cubic yard, so cubic feet are divided by 27 after volume is calculated.
Bag count80 lb bag yield estimate
The bag estimate uses about 0.6 cubic feet per 80 lb bag and rounds up. Check the specific product label before buying.
Source notes
References used for this calculator
Benchmarks
How to read the result
2 in: Light overlay.
Usually too thin for structural slabs unless specified by a pro.
4 in: Common 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
Formula, inputs, limitations and review record
Formula
Concrete volume = length x width x depth after converting all dimensions to one base unit
Inputs used
Feet or meters, Length, Width, Depth, Waste percent, Price per volume
Limitations
Home-material calculators estimate quantity and cost from visible dimensions and coverage assumptions. They do not replace field measurement, installer guidance, structural design, permits, or code review.
Review record
Catalog QA baseline on June 6, 2026. This date marks the catalog-wide automated and editorial QA baseline, not a tool-specific expert review.
Cite this page
Toolkit Shelf. Concrete Calculator. 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.
Does this calculate reinforcement or permits?
No. It estimates concrete volume, bag count, and material cost. Reinforcement, subbase, drainage, permits, and structural design need separate planning.
Can I use this for a driveway or structural slab?
Use it only for a rough volume estimate. Driveways, load-bearing slabs, and code-sensitive work should be checked by a qualified contractor or engineer.
Why should I add a material buffer?
Cuts, waste, damaged pieces, uneven surfaces, pattern matching, delivery limits, and field measurements can all make the exact calculated amount too low.
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