Estimate concrete volume in cubic feet for slabs, round pads, strip footings and post holes. Enter your own feet-and-inches measurements, add a practical waste allowance, and compare the same quantity in cubic yards and cubic metres with an optional concrete-only cost estimate.
All number fields are blank. The faded zero is only a placeholder, so typing 6 gives you 6 — not 06.
Your result will appear after you press Calculate Cubic Feet.
For a rectangular slab, convert thickness from inches to feet, then multiply length × width × depth.
The calculator keeps cubic feet, cubic yards, cubic metres, waste and cost easy to compare.
See the main project volume in cubic feet.
Convert cubic feet to the common ready-mix ordering unit.
Compare the same quantity in metric units.
Add a practical percentage for site variation.
Enter your own concrete rate for a material-only estimate.
Save the project measurements and converted quantities.
A Concrete Cubic Feet Calculator converts three-dimensional project measurements into cubic feet. Cubic feet are useful for small concrete volumes, material comparisons and converting a project into cubic yards. The most important step is making sure thickness or depth is included; square feet alone do not describe concrete volume.
Cubic Feet = Length (ft) × Width (ft) × Thickness (ft)If thickness is measured in inches, divide it by 12 first. A 4-inch slab is 0.3333 ft thick. A 10 ft × 10 ft slab at 4 inches thick therefore contains approximately 33.33 ft³ before waste.
Mixing feet and inches directly is one of the most common concrete volume mistakes. A depth of 6 inches is 0.5 ft, not 6 ft. The calculator performs this conversion automatically for slab thickness, footing width and depth, and post-hole measurements.
| Thickness | Depth In Feet | ft³ Per 100 ft² | yd³ Per 100 ft² |
|---|---|---|---|
| 3 in | 0.250 ft | 25.00 ft³ | 0.93 yd³ |
| 4 in | 0.333 ft | 33.33 ft³ | 1.23 yd³ |
| 5 in | 0.417 ft | 41.67 ft³ | 1.54 yd³ |
| 6 in | 0.500 ft | 50.00 ft³ | 1.85 yd³ |
| 8 in | 0.667 ft | 66.67 ft³ | 2.47 yd³ |
One cubic yard equals 27 cubic feet because one yard is 3 feet and 3 × 3 × 3 = 27. Divide cubic feet by 27 to convert to cubic yards.
Cubic Yards = Cubic Feet ÷ 27| Cubic Feet | Cubic Yards | Approx. Cubic Metres |
|---|---|---|
| 9 ft³ | 0.33 yd³ | 0.25 m³ |
| 13.5 ft³ | 0.50 yd³ | 0.38 m³ |
| 27 ft³ | 1.00 yd³ | 0.76 m³ |
| 54 ft³ | 2.00 yd³ | 1.53 m³ |
| 135 ft³ | 5.00 yd³ | 3.82 m³ |
A round pad is a cylinder. Enter diameter in feet and depth in inches. The calculator converts the depth to feet and calculates π × radius² × depth. If several identical pads are required, multiply by the quantity.
Cubic Feet = π × Radius² × Depth (ft) × QuantityStrip footings use length × width × depth. Enter total length in feet and width and depth in inches. If the footing changes size, calculate each section separately and add the cubic-foot results.
Post holes are cylinders. Enter hole diameter and depth in inches plus the number of holes. The calculator also includes a simple optional post-displacement adjustment.
Waste allowance is applied after the geometric volume has been calculated. A 100 ft³ base volume becomes 105 ft³ with 5% waste, 110 ft³ with 10%, and 115 ft³ with 15%.
| Base Volume | 5% Waste | 10% Waste | 15% Waste |
|---|---|---|---|
| 10 ft³ | 10.5 ft³ | 11.0 ft³ | 11.5 ft³ |
| 25 ft³ | 26.25 ft³ | 27.5 ft³ | 28.75 ft³ |
| 50 ft³ | 52.5 ft³ | 55.0 ft³ | 57.5 ft³ |
| 100 ft³ | 105 ft³ | 110 ft³ | 115 ft³ |
Ready-mix pricing is commonly quoted per cubic yard, so the calculator converts the volume with waste to cubic yards before applying the rate you enter.
Estimated Concrete Cost = Cubic Yards With Waste × Price Per Cubic YardThis is a concrete-only estimate. Delivery, short-load fees, pump hire, reinforcement, excavation, formwork, labour and finishing may be separate. Use the Concrete Cost Calculator for broader budgeting and the Concrete Order Calculator for supplier minimums and truck-load planning.
| Project | Dimensions | Base ft³ | Base yd³ | With 10% Waste |
|---|---|---|---|---|
| Small Slab | 8 ft × 8 ft × 4 in | 21.33 | 0.79 | 23.47 ft³ |
| 10 × 10 Slab | 10 ft × 10 ft × 4 in | 33.33 | 1.23 | 36.67 ft³ |
| Patio | 12 ft × 16 ft × 4 in | 64.00 | 2.37 | 70.40 ft³ |
| Footing | 40 ft × 12 in × 12 in | 40.00 | 1.48 | 44.00 ft³ |
The light zero inside each field is only a placeholder. The field itself is empty, so typing 10 gives 10 rather than 010. Reset clears the field and shows the faded placeholder again.
Cubic feet are especially useful for checking smaller concrete quantities and for understanding the volume before converting to cubic yards. Because a cubic yard contains 27 cubic feet, you can move easily between the two units once the base volume is known.
For slabs, surface area multiplied by thickness in feet gives cubic feet. A 200 ft² slab at 4 inches thick contains about 66.67 ft³. At 6 inches thick, the same area contains 100 ft³. This shows why slab thickness has a large effect on material quantity.
Driveways often have changing widths and aprons. Break them into smaller rectangles and calculate each section. A dedicated Driveway Concrete Calculator can also be used for a focused driveway estimate.
Footing trenches can vary more than formed slabs. Measure the actual prepared trench in several locations, especially when excavation walls are irregular. If footing size changes, calculate each section separately.
Small post-hole volumes become significant when many holes are involved. Use the exact number of holes and measure more than one prepared hole where ground conditions vary.
One cubic foot is approximately 0.0283168 cubic metres. The calculator converts your volume automatically so metric plans or product data can be compared with imperial site measurements.
| Cubic Feet | Approx. Cubic Metres | Cubic Yards |
|---|---|---|
| 10 ft³ | 0.28 m³ | 0.37 yd³ |
| 25 ft³ | 0.71 m³ | 0.93 yd³ |
| 50 ft³ | 1.42 m³ | 1.85 yd³ |
| 100 ft³ | 2.83 m³ | 3.70 yd³ |
| 250 ft³ | 7.08 m³ | 9.26 yd³ |
The Concrete Yard Calculator focuses on cubic yards as the main result. This page focuses on ft³ first, which can be more intuitive for smaller imperial-unit projects. Both tools use the same underlying volume relationships.
Recalculate after dimensions change, after excavation, after forms are set, or whenever the waste allowance or supplier rate changes. A final calculation made immediately before ordering is usually more useful than an early rough estimate.
For concrete technical education and industry resources, visit the American Concrete Institute. For U.S. workplace information about respirable crystalline silica, review OSHA silica guidance. Use project-specific drawings, specifications and supplier information for the actual job.
Cubic feet are especially useful when a concrete project is measured primarily in feet and inches. Small slabs, steps, footings, fence-post holes and repair areas can often be understood more easily in ft³ before the volume is converted into cubic yards for ordering. Keeping the cubic-foot result visible also gives you a quick way to check whether the final yardage makes sense.
Suppose a pad measures 6 ft long, 4 ft wide and 4 inches thick. Convert 4 inches to 0.333 ft, then multiply 6 × 4 × 0.333. The result is approximately 8 ft³ before waste. That is only about 0.30 yd³, which immediately tells you the project is much smaller than a full cubic yard.
For a 12 ft × 12 ft patio at 4 inches thick, the base volume is 48 ft³. Dividing by 27 gives approximately 1.78 yd³. If the prepared base varies slightly, adding a practical waste allowance can help you see the planning quantity before supplier rounding.
Long narrow walkways are easy to calculate in cubic feet because the dimensions are often given in feet with thickness in inches. A 30 ft long path that is 3 ft wide and 4 inches thick has a base volume of 30 ft³. If the width changes along the path, split the walkway into sections rather than relying on one average width.
Steps can be estimated by treating each step as a small rectangular prism. Calculate tread length × tread width × step depth, then add the individual step volumes. Be careful with overlapping geometry; if a stair is cast as one monolithic shape, the actual volume may need to be broken into stacked prisms rather than counting the same space twice.
Footings are often measured in feet for length and inches for width and depth. This makes ft³ a natural intermediate unit. A 20 ft footing that is 12 inches wide and 12 inches deep contains 20 ft³. If the footing widens or deepens in certain sections, calculate those portions separately.
Post-hole projects can involve relatively small volumes per hole but many repeated holes. A small difference in hole diameter can make a noticeable difference when multiplied by 10, 20 or 30 posts. Measure actual hole dimensions rather than relying only on the nominal auger size.
Round columns and piers use the cylinder formula. Radius is half the diameter, and volume equals π × radius² × height. When diameter is given in inches, convert it to feet before calculating if you want a cubic-foot result.
For a rectangular slab, calculate the surface area in square feet first, then multiply by thickness in feet. If a 150 ft² slab is 4 inches thick, thickness is 0.333 ft, so the volume should be close to 50 ft³. This area-times-depth check is a quick way to catch obvious input mistakes.
| Slab Area | 3 in Thick | 4 in Thick | 5 in Thick | 6 in Thick |
|---|---|---|---|---|
| 50 ft² | 12.50 ft³ | 16.67 ft³ | 20.83 ft³ | 25.00 ft³ |
| 100 ft² | 25.00 ft³ | 33.33 ft³ | 41.67 ft³ | 50.00 ft³ |
| 200 ft² | 50.00 ft³ | 66.67 ft³ | 83.33 ft³ | 100.00 ft³ |
| 500 ft² | 125.00 ft³ | 166.67 ft³ | 208.33 ft³ | 250.00 ft³ |
One extra inch of slab thickness can add a surprisingly large amount of concrete when the area is large. On a 500 ft² slab, increasing thickness from 4 inches to 5 inches adds about 41.67 ft³, which is more than 1.5 cubic yards. This is why thickness should come from the project design rather than from a casual estimate.
Ready-mix is generally discussed in cubic yards in the United States, so use cubic feet as the calculation basis and cubic yards as the supplier comparison unit. Once the final cubic-foot volume with waste is known, divide by 27 and then follow the supplier's accepted order increment and minimum-load rules.
For very small projects, packaged concrete may be easier than ready-mix. To compare, you need the finished yield per bag from the exact product. Do not assume a fixed yield based only on bag weight. The Concrete Bags Needed Calculator is better suited to whole-bag planning.
Irregular shapes should usually be divided into smaller rectangles, circles or cylinders. Calculate each piece in cubic feet and add the volumes. A sketch with labeled dimensions can make the takeoff much easier to verify and can help prevent both missing areas and double-counted overlaps.
A slab may have a general thickness across most of its area but deeper perimeter edges, beams or ribs. Calculate the main slab first, then add only the extra volume of the deeper sections. This avoids counting the base slab thickness twice.
If concrete is placed directly against earth, the prepared excavation dimensions may matter more than the nominal design outline for quantity planning. Excavations can widen, slump or deepen. Measure the actual space where practical while still following all required structural dimensions.
The calculator rounds the final planning quantity upward to the increment you select. Upward rounding avoids showing a number below the calculated requirement merely because of normal rounding. Supplier-specific ordering rules should still be confirmed separately.
If you enter a price per cubic yard, the calculator converts the volume with waste into yd³ before estimating concrete-only cost. This keeps the cost logic aligned with common ready-mix pricing while still showing ft³ as the main volume result.
An early calculation is useful during budgeting. A second calculation after drawings or dimensions are confirmed can improve planning. A final calculation after formwork or excavation is prepared gives you the best opportunity to compare the real site with the planned dimensions before ordering concrete.
The calculator estimates concrete-only cost from your entered rate, while a complete project budget can include many other items.
Use related tools for cubic yards, ready-mix ordering and broader concrete estimating.
Common questions about ft³, cubic yards, slab thickness, footings, post holes, waste and cost.
For a rectangular slab, multiply length in feet by width in feet by thickness in feet. If thickness is entered in inches, divide it by 12 before multiplying.
Yes. The calculator accepts slab thickness in inches and converts it to feet automatically.
One cubic yard equals 27 cubic feet.
Yes. The result area shows both cubic feet and cubic yards.
Yes. The result includes cubic metres so you can compare imperial and metric volume.
Yes. Select Round Pad and enter diameter, depth and the number of identical pads.
Yes. Enter total footing length in feet and footing width and depth in inches.
Yes. Enter hole diameter and depth in inches plus the number of holes.
The zero is only a placeholder. The actual field is blank, so typing 8 produces 8 rather than 08.
Yes. Enter your own percentage and the calculator adds it before showing the planning quantity.
Yes. Enter your own price per cubic yard. The cost is a concrete-only estimate and may not include delivery, pumping, labour or other project charges.
Yes. After calculating, you can download a PDF summary generated by ConcreteCreek.com.
Use current project documents, supplier information and official safety guidance alongside any online estimate.
Concrete technical education and industry resources.
Visit ACIU.S. workplace information about respirable crystalline silica.
Read OSHA GuidanceConfirm cubic-yard increments, minimum loads, delivery requirements and current pricing.
Use required dimensions, concrete strength, reinforcement and construction details.