Concrete Calculator
Measure the pour. Estimate the concrete. Plan with confidence.
Enter your concrete project dimensions and material details. We’ll estimate cubic feet, cubic yards, bags needed and material cost.
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About the Creator
MyCruncher — Founded by Bobby Dues
MyCruncher provides free online calculators designed to make everyday calculations easier to understand and use.
Meet Bobby Dues →Free Concrete Calculator – Estimate Cubic Yards, Bags and Material Cost
Planning a concrete project? The free MyCruncher Concrete Calculator helps estimate the amount of concrete needed for rectangular slabs, patios, walkways, and other projects.
Enter your project length, width, thickness, waste allowance, bag size, and material pricing information to estimate concrete volume in cubic feet and cubic yards.
Whether you're preparing a backyard patio, sidewalk, shed pad, or another concrete project, knowing the estimated volume can help you compare material options and prepare your budget.
The calculator provides preliminary material estimates. Actual construction requirements depend on project design, soil conditions, structural loads, and applicable building codes.
How to Use the Concrete Calculator
The MyCruncher Concrete Calculator uses your project dimensions and material selections to estimate concrete quantities.
- Enter the length. Measure the rectangular concrete area and enter its length in feet.
- Enter the width. Provide the width in feet. Length and width establish the surface area.
- Enter the thickness. Provide the planned concrete thickness in inches. Use a thickness appropriate for the actual project design.
- Choose a waste allowance. Select an additional percentage to account for expected waste, spillage, uneven excavation, and other volume differences.
- Select a concrete bag size. Choose a bag size when estimating packaged concrete. Verify the mixed yield printed on the exact product packaging.
- Select the pricing method. Choose the available method that matches your concrete purchase, such as pricing by cubic yard.
- Enter your material price. Use a supplier quote or current store price for the selected pricing method.
- Click Calculate Concrete. The calculator estimates the required volume and material quantities.
- Review your results. Check the estimated cubic feet, cubic yards, bags needed, and material cost.
You can adjust the dimensions, thickness, waste, bag selection, or pricing to compare different project scenarios.
How Do You Calculate Concrete Cubic Feet?
Concrete volume is calculated by multiplying the length, width, and thickness of the space being filled.
If length and width are in feet but thickness is in inches, divide the thickness by 12 before multiplying.
For example, suppose a slab measures 10 feet long, 10 feet wide, and 4 inches thick.
The required concrete volume before waste is approximately 33.33 cubic feet.
How Do You Convert Cubic Feet to Cubic Yards?
Ready-mix concrete is commonly ordered by the cubic yard.
One cubic yard equals 27 cubic feet.
To convert cubic feet into cubic yards, divide the cubic-foot volume by 27.
For our 33.33-cubic-foot example:
The concrete volume before waste is approximately 1.23 cubic yards.
Concrete Calculation Example
Example: Suppose you're planning a rectangular concrete patio measuring 10 feet by 10 feet.
The planned slab thickness is 4 inches, and you want a 10% extra material allowance.
Example Project Information
- Length: 10 feet
- Width: 10 feet
- Thickness: 4 inches
- Waste Allowance: 10%
- Example Bag Size: 80 lb
- Standard Bag Yield: 0.60 cu ft
Step 1: Calculate Surface Area
Multiply the length by the width.
The slab surface area is 100 square feet.
Step 2: Convert Thickness to Feet
Divide the 4-inch thickness by 12.
Step 3: Calculate Cubic Feet
Multiply the surface area by the thickness in feet.
The slab requires approximately 33.33 cubic feet before waste.
Step 4: Add the Waste Allowance
Multiply the original volume by 1.10 for an additional 10%.
The adjusted concrete volume is approximately 36.67 cubic feet.
Step 5: Convert to Cubic Yards
Divide the adjusted volume by 27.
Step 6: Estimate 80-Pound Bags
For standard concrete mix yielding approximately 0.60 cubic feet per 80-pound bag, divide the required volume by the bag yield.
Round up to whole bags.
The preliminary estimate is 62 bags of standard 80-pound concrete mix.
Step 7: Estimate Cubic-Yard Material Cost
Suppose a concrete supplier quotes a hypothetical $180 per cubic yard, before delivery and other charges.
Multiply the unrounded volume including waste by $180.
The illustrative material-only cost is approximately $244.44.
Actual ready-mix suppliers may impose minimum orders, short-load charges, delivery fees, and other expenses.
Concrete Calculation Example Summary
| Calculation | Illustrative Result |
|---|---|
| Surface Area | 100 sq ft |
| Slab Thickness | 4 inches |
| Volume Before Waste | 33.33 cu ft |
| Waste Allowance | 10% |
| Volume With Waste | 36.67 cu ft |
| Cubic Yards With Waste | 1.36 cu yd |
| 80 lb Bag Yield | 0.60 cu ft |
| Estimated 80 lb Bags | 62 |
| Example Price Per Yard | $180 |
| Example Ready-Mix Material Cost | $244.44 |
This example demonstrates how project dimensions, concrete thickness, waste, and material pricing can be combined into a preliminary estimate.
These quantities assume a uniform 4-inch thickness and 10% extra volume. The bag calculation uses the published 0.60-cubic-foot yield of common 80-pound concrete mixes. Actual product yields, supplier ordering increments, and material requirements may differ.
Concrete Volume Chart by Slab Size
The following table estimates concrete quantities for several rectangular slabs at a uniform 4-inch thickness.
Every result includes a 10% extra material allowance.
| Slab Size | Cubic Feet | Cubic Yards | 80 lb Bags |
|---|---|---|---|
| 5 × 5 ft | 9.17 | 0.34 | 16 |
| 8 × 10 ft | 29.33 | 1.09 | 49 |
| 10 × 10 ft | 36.67 | 1.36 | 62 |
| 10 × 12 ft | 44.00 | 1.63 | 74 |
| 12 × 12 ft | 52.80 | 1.96 | 88 |
| 12 × 16 ft | 70.40 | 2.61 | 118 |
| 15 × 20 ft | 110.00 | 4.07 | 184 |
Bag estimates use a 0.60-cubic-foot yield per 80-pound bag and are rounded up.
The cubic-yard values are displayed to two decimal places.
Larger pours may be more practical with ready-mix delivery instead of individual bags.
On smaller mobile screens, swipe horizontally inside the table to view all columns. The slab thicknesses shown are estimating assumptions, not structural design recommendations.
How Does Concrete Thickness Affect Cubic Yards?
Concrete thickness directly affects the amount of material required.
A thicker slab requires more concrete even when its length and width remain unchanged.
10-by-10-Foot Slab Thickness Comparison
The following table uses a 100-square-foot area and a 10% extra allowance.
| Thickness | Cubic Yards | 80 lb Bags |
|---|---|---|
| 3 inches | 1.02 | 46 |
| 4 inches | 1.36 | 62 |
| 5 inches | 1.70 | 77 |
| 6 inches | 2.04 | 92 |
| 8 inches | 2.72 | 123 |
These examples show how concrete volume increases with thickness.
The appropriate structural thickness depends on the project, loads, reinforcement, subgrade, and building requirements.
Do not select a thickness solely because a particular quantity appears affordable.
How Much Concrete Is in an 80-Pound Bag?
Many standard 80-pound premixed concrete products yield approximately 0.60 cubic feet of finished concrete.
The yield is the volume of mixed concrete, not the dry volume of the bag.
For example, one cubic yard contains 27 cubic feet.
Divide 27 by 0.60 to estimate the number of standard 80-pound bags per yard.
Approximately 45 standard 80-pound bags produce one cubic yard, before any extra allowance.
Specialty concrete products may have different yields, so always consult the manufacturer's product information.
Concrete Bag Size and Yield Chart
The following table uses published approximate yields for standard QUIKRETE Concrete Mix products.
| Bag Size | Yield Per Bag | Bags Per Cubic Yard |
|---|---|---|
| 40 lb | 0.30 cu ft | 90 |
| 50 lb | 0.375 cu ft | 72 |
| 60 lb | 0.45 cu ft | 60 |
| 80 lb | 0.60 cu ft | 45 |
These are common standard concrete mix yields, not guaranteed values for every product.
Always use the yield printed on the exact bag or manufacturer's technical data sheet.
For official yield information, see the QUIKRETE Concrete Mix Product Data Sheet .
How Many Bags of Concrete Do I Need?
To calculate the number of concrete bags required, divide the concrete volume in cubic feet by the finished yield per bag.
Round the resulting number upward because bags are normally purchased as whole units.
Example Using 60-Pound Bags
Suppose you need 36.67 cubic feet of concrete including waste.
A standard 60-pound bag yields approximately 0.45 cubic feet.
Example Using 80-Pound Bags
For the same volume, a standard 80-pound bag yields approximately 0.60 cubic feet.
Larger bags generally reduce the number of individual bags that must be mixed, but each bag is heavier.
Concrete Bag Quantity Comparison
The following comparison uses a total required volume of approximately 36.67 cubic feet, including the 10% allowance.
| Bag Size | Approximate Yield | Bags Needed |
|---|---|---|
| 40 lb | 0.30 cu ft | 123 |
| 50 lb | 0.375 cu ft | 98 |
| 60 lb | 0.45 cu ft | 82 |
| 80 lb | 0.60 cu ft | 62 |
These values use the same estimated concrete requirement, but different standard bag yields.
The correct bag count depends on the specific product being purchased.
What Is a Concrete Waste Allowance?
A concrete waste allowance adds extra volume to the calculated dimensions.
It may help account for small spills, uneven forms, ground irregularities, and other differences between planned and actual concrete requirements.
A 10% allowance is one commonly used preliminary estimating option.
However, the proper amount depends on the project and site conditions.
Concrete Waste Formula
Waste Allowance Example
Suppose a slab requires 33.33 cubic feet before waste.
Adding 10% increases the approximate required volume to 36.67 cubic feet.
Concrete Waste Allowance Comparison
The following table uses a 10-by-10-foot slab with a 4-inch thickness.
| Extra Allowance | Cubic Feet | Cubic Yards |
|---|---|---|
| 0% | 33.33 | 1.23 |
| 5% | 35.00 | 1.30 |
| 10% | 36.67 | 1.36 |
| 15% | 38.33 | 1.42 |
| 20% | 40.00 | 1.48 |
A larger allowance increases material quantity and potential cost.
Actual requirements should be based on measured conditions, not only a fixed percentage.
How Much Does Concrete Cost Per Cubic Yard?
Concrete prices vary based on location, supplier, mix design, order quantity, delivery requirements, and other factors.
The MyCruncher calculator allows you to enter material pricing rather than relying on a single assumed market price.
Concrete Cost Formula
For example, suppose a project requires 1.358 cubic yards including waste.
At an illustrative material price of $180 per cubic yard:
This estimate does not include delivery charges, short-load fees, taxes, or other project expenses.
Concrete Price Comparison Table
The following table compares hypothetical concrete prices using approximately 1.358 cubic yards of material.
| Price Per Cubic Yard | Material Cost |
|---|---|
| $150 | $203.70 |
| $180 | $244.44 |
| $200 | $271.60 |
| $225 | $305.56 |
| $250 | $339.51 |
These are illustrative mathematical examples, not current supplier quotes.
Actual material charges may depend on minimum order quantities and supplier rounding policies.
Bagged Concrete vs. Ready-Mix Concrete
Concrete can be purchased in individual bags or delivered in bulk by a ready-mix supplier.
The most suitable option depends on the project size, site accessibility, labor available, mixing equipment, and total cost.
Bagged Concrete
Bagged concrete is commonly used for smaller projects, repairs, posts, and other applications where individual mixing batches may be practical.
Larger projects can require many heavy bags and substantial mixing time.
Ready-Mix Concrete
Ready-mix concrete is supplied in bulk from a concrete production facility.
It may be practical for larger continuous pours, depending on site access, supplier availability, and delivery charges.
Material Cost Comparison Example
For our 10-by-10-foot slab, suppose you compare the following hypothetical prices.
| Purchase Option | Example Material Cost |
|---|---|
| 62 Bags at $7.50 | $465.00 |
| 1.358 yd³ at $180/yd³ | $244.44 |
This compares only illustrative concrete material charges.
Ready-mix delivery, short-load fees, minimum orders, labor, and equipment can significantly change the final comparison.
Bagged material prices also vary by retailer and product.
How Much Concrete Is Needed for a Patio?
A rectangular patio's concrete volume depends on its length, width, and specified thickness.
For example, a 12-by-12-foot patio has an area of 144 square feet.
At an illustrative 4-inch thickness:
Convert to cubic yards.
With 10% extra material:
This is a volume example, not a recommendation that every patio should be 4 inches thick.
How Much Concrete Is Needed for a Walkway?
Walkway material estimates can be calculated using the same rectangular volume formula.
Suppose a walkway is 20 feet long and 3 feet wide.
At an illustrative 4-inch thickness:
Convert to cubic yards.
With 10% extra:
Actual walkway thickness and construction details should follow the project requirements.
How Do You Calculate Concrete for a Footing?
Rectangular footings can be estimated using length, width, and depth.
All dimensions must use compatible units before calculating volume.
For example, a rectangular footing measuring 6 feet long, 2 feet wide, and 1 foot deep has a volume of:
That equals approximately 0.44 cubic yards before waste.
Structural footing dimensions are determined by load requirements, soil conditions, engineering, and applicable codes.
The example provides volume arithmetic only and does not determine suitable footing dimensions.
How Do You Calculate Concrete for Round Post Holes?
Round post holes have a cylindrical shape rather than a rectangular shape.
A cylinder's volume can be calculated using the radius and depth.
The radius is one-half the hole diameter.
For example, a 12-inch-diameter hole has a radius of 6 inches, or 0.5 feet.
If the hole is 2 feet deep, the full cylindrical volume is:
The actual concrete volume may be smaller if a post or other object displaces part of the cylinder.
Calculate the displaced volume when appropriate and follow the project's structural and installation requirements.
The basic MyCruncher Concrete Calculator uses rectangular length, width, and thickness inputs.
Round holes may require a separate manual volume calculation.
Why Is Concrete Thickness Important?
Concrete thickness affects both the volume of concrete needed and the structural performance of the finished work.
A thicker slab generally uses more concrete than a thinner slab with the same surface area.
However, correct thickness also depends on expected loading, soil support, reinforcement, joint design, and other requirements.
A walkway, vehicle driveway, equipment pad, and structural footing may have different design requirements.
The Concrete Calculator does not determine structural suitability or building-code compliance.
What Other Materials May Be Needed for a Concrete Project?
Concrete volume is only one part of a complete construction estimate.
Additional project materials and services may include:
- Gravel or aggregate base. Used where the project design requires a prepared base.
- Form boards. Used to contain and shape concrete during placement.
- Reinforcement. Rebar, welded wire, or other reinforcement when specified by the design.
- Control joints. Planned joints used to help manage concrete cracking.
- Expansion or isolation joints. Used where required by the project design.
- Finishing materials. Products or equipment used to obtain the desired surface.
- Curing materials. Products or methods used to maintain suitable curing conditions.
- Labor. Preparation, mixing, placement, finishing, and cleanup.
- Equipment. Mixers, tools, compactors, wheelbarrows, or placement equipment.
- Permits and inspections. Applicable local construction requirements.
These items should be estimated separately when preparing a complete project budget.
Why Are Concrete Curing Conditions Important?
Concrete curing supports the development of strength and durability after placement.
Moisture and temperature are important factors during the curing process.
Excessively hot, cold, dry, or windy conditions can affect curing and surface performance.
Follow the chosen concrete product's mixing, placement, finishing, and curing instructions.
Do not assume a surface that appears dry has reached its required design strength.
Concrete Mixing Safety Tips
Concrete materials can present chemical, dust, lifting, and equipment hazards.
- Wear protective gloves. Wet concrete can cause chemical burns and skin irritation.
- Protect your eyes. Use appropriate eye protection when handling and mixing materials.
- Control dust exposure. Follow the product's safety instructions when opening and mixing dry bags.
- Use safe lifting practices. Concrete bags are heavy and can cause injury if handled improperly.
- Follow mixing instructions. Use the water amount and mixing method specified for the selected product.
- Prepare the work area. Make sure the forms, tools, and material delivery plan are ready before placement.
- Observe weather requirements. Take appropriate measures for hot or cold conditions.
Review the manufacturer's Safety Data Sheet and instructions before handling concrete.
Helpful Tips for Estimating Concrete Accurately
- Measure carefully. Confirm project length, width, and thickness.
- Use the correct units. Convert inches to feet before calculating cubic feet.
- Check finished dimensions. Calculate the actual space to be filled.
- Allow for site conditions. Uneven excavation or irregular forms may affect volume.
- Use the correct bag yield. Verify the finished volume printed on the exact concrete product.
- Compare bags with delivery. Consider total material, transportation, equipment, and labor costs.
- Get current supplier quotes. Concrete prices can vary by location and mix type.
- Check structural requirements. Confirm specified thickness, reinforcement, and support conditions.
- Prepare the pour. Plan mixing, transportation, placement, and finishing ahead of time.
- Confirm the final order. Review quantities with the supplier or qualified professional before purchasing.
Frequently Asked Questions
How do I calculate concrete cubic yards?
Multiply length by width and thickness using compatible units, then divide cubic feet by 27.
How many cubic feet are in one cubic yard?
One cubic yard equals exactly 27 cubic feet.
How many cubic yards are needed for a 10-by-10 slab?
At an illustrative 4-inch thickness, a 10-by-10-foot slab requires approximately 1.23 cubic yards before waste.
With 10% extra, the estimate becomes approximately 1.36 cubic yards.
How much concrete is needed for a 12-by-12 slab?
At an illustrative 4-inch thickness, a 12-by-12-foot slab requires approximately 1.78 cubic yards before waste.
With 10% extra, the estimate is approximately 1.96 cubic yards.
How many 80-pound concrete bags make a cubic yard?
Approximately 45 standard 80-pound bags yielding 0.60 cubic feet each produce one cubic yard.
How much concrete does an 80-pound bag make?
Many standard 80-pound concrete mixes yield approximately 0.60 cubic feet of finished concrete.
Always verify the product label or data sheet.
How much concrete does a 60-pound bag make?
A standard 60-pound concrete mix commonly yields approximately 0.45 cubic feet.
How many 60-pound concrete bags make a yard?
Approximately 60 standard 60-pound bags yielding 0.45 cubic feet each make one cubic yard.
How many bags do I need for a 10-by-10 slab?
At a 4-inch thickness with 10% extra, the illustrated 10-by-10-foot slab requires about 62 standard 80-pound bags yielding 0.60 cubic feet each.
How do I calculate concrete bags?
Divide the adjusted concrete volume in cubic feet by the yield per bag.
Round the result up to the next whole bag.
Does the calculator include waste?
Yes. MyCruncher includes a Waste Allowance field for adding extra material to the calculated volume.
Is a 10% concrete waste allowance enough?
It may be suitable for some preliminary estimates, but actual conditions can require more or less material.
Confirm the volume and allowance for your specific project.
Does the calculator convert cubic feet to cubic yards?
Yes. The calculator estimates concrete quantities in cubic feet and cubic yards.
What is the formula for a concrete slab?
Multiply length in feet by width in feet and thickness in feet.
When thickness is entered in inches, divide it by 12.
How much does one cubic yard of concrete cost?
Prices vary by supplier, mix, location, order quantity, and delivery requirements.
Use an actual supplier price in the calculator for a relevant material estimate.
Is ready-mix cheaper than concrete bags?
Sometimes, particularly for larger pours.
However, ready-mix delivery, minimum orders, equipment, and labor can change the comparison.
Does the calculator include concrete delivery fees?
A basic price-per-cubic-yard calculation should not be assumed to include delivery or short-load charges unless those amounts are included in the entered price.
Can I calculate concrete for a patio?
Yes. Enter the rectangular patio dimensions and specified thickness to estimate volume.
Can I calculate concrete for a sidewalk?
Yes. Rectangular walkways can be estimated using length, width, and thickness.
Can I calculate concrete for a driveway?
The calculator can estimate the volume of a rectangular driveway.
Driveway thickness, reinforcement, base preparation, and structural design must be determined separately.
Can I calculate concrete for footings?
You can estimate rectangular footing volume using compatible dimensions.
The calculator does not design or approve structural footings.
Can I calculate concrete for round fence post holes?
Round holes use a cylindrical volume formula.
The rectangular Concrete Calculator does not separately provide a round-hole input in the layout described here.
Does the calculator include reinforcement?
No. Rebar, wire reinforcement, and other structural materials must be estimated separately.
Does the calculator include gravel base?
No. Gravel, subbase preparation, and other foundation materials require separate calculations.
Does the calculator determine correct slab thickness?
No. It calculates concrete volume using the thickness you enter.
Actual thickness requirements depend on project design, loading, and applicable codes.
Why might my concrete supplier recommend more material?
Suppliers may account for ordering increments, uneven ground, form dimensions, spillage, and other project conditions.
Do I need a permit for concrete work?
Permit requirements depend on the project and local jurisdiction.
Contact your building department when necessary.
Are concrete calculator estimates guaranteed?
No. Actual quantities and costs may differ because of measurements, site conditions, product yields, pricing, and other factors.
Is the MyCruncher Concrete Calculator free?
Yes! The MyCruncher Concrete Calculator is free to use for preliminary concrete volume, bag quantity, and material cost estimates.
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For official concrete mix and bag yield information, visit the QUIKRETE Concrete Mix Technical Data Sheet .
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Important: The MyCruncher Concrete Calculator provides preliminary educational material and cost estimates. Actual requirements can vary due to measurements, uneven subgrade, waste, bag yields, site conditions, material pricing, and supplier policies. The calculator does not determine structural design, reinforcement, proper slab thickness, foundation suitability, or building-code compliance. Confirm final quantities and construction requirements with suppliers and qualified professionals when appropriate. Follow product-specific mixing, placement, curing, and safety instructions.