Estimate concrete volume.
Bag yields are approximate; verify the manufacturer’s stated yield.
Concrete volume = Length × Width × Depth
Order quantity = Volume × (1 + Waste allowance)The calculation converts entered dimensions into area or volume, then applies coverage, pack size, coats or waste where supported. Openings, slopes, pattern matching, uneven surfaces and manufacturer coverage can change the final purchase quantity.
Concrete Calculator This tool will tell you how much concrete is needed for everyday job like slabs, footings, sidewalks, pads and other rectangular or round projects. You will need to fill in the dimensions of the length, width & depth OR the required dimensions for the selected geometry. This calculator can provide the volume either cubic yards or cubic feet based on available dimensions inputs & outputs.
The quantity is only an estimate to help with ordering materials and does need to compensate for the job and/or form dimensions and expected waste. Follow your concrete supplier’s recommendation.
Note down the size of the area to be filled with concrete and include the dimensions in uniform units. American conventional measurements such as feet and inches are frequently used for a home construction project.
For non-regular project, breakdown the area into a few smaller portion which form simpler shape. Sum up volumes of each portions instead of attempting to use one set of dimension to approximate the entire project.
It is a concrete calculator which calculates how much space must be filled. If the shape is rectangular it takes the length by the width by the depth and then converts it to the right unit.
In the U.S., people order their concrete by cubic yards. Remember that a cubic yard is equivalent to 27 cubic feet. A calculation in cubic feet simply can be divided by 27 to convert to cubic yards.
This is an estimate, in mathematical terms, provided by the calculator. Site conditions, excavation and form changes, waste, spillage, undulations, and contractor needs should be considered when placing the order.
For a rectangular slab or footing, the basic volume formula is:
Volume = Length × Width × Thickness
When all three dimensions are measured in feet, the result is cubic feet.
To convert cubic feet to cubic yards:
Cubic Yards = Cubic Feet ÷ 27
If the thickness is measured in inches, convert it to feet first:
Thickness in Feet = Thickness in Inches ÷ 12
For example, a 4-inch slab has a thickness of 4 ÷ 12 = 0.3333 feet.
Suppose you are planning a rectangular concrete patio that is 20 feet long, 12 feet wide, and 4 inches thick.
First calculate the volume:
20 × 12 × 0.3333 = approximately 80 cubic feet
Then convert cubic feet to cubic yards:
80 ÷ 27 = approximately 2.96 cubic yards
The simple mathematical calculation is thus around 2.96 cubic yards concrete before accounting for job waste. The real order should reflect the final project shape dimension and the advice from concrete supplier.
The resulting volume should be treated as an estimate of the volume which is ideally required. To avoid under- ordering we generally estimate on a slight over order. This accounts for variations in excavations and formwork.
Factors that can affect the amount include:
Yourconcrete supplier or concrete contractorcan assist you in establishing the correct quantity to order for your job. There isnoset waste factorthat should be applied to every job; it will depend on shape of project, preparation, accessibility and what material will be used to place concret.
The basic length-by-width-by-depth formula applies to rectangular spaces. Other shapes require different volume formulas.
For patios, walkways, floors, and pads with rectangular dimensions, multiply length by width by thickness.
A cylindrical form uses the cylinder volume formula:
Volume = π × Radius² × Height
The radius is half the diameter. Make sure all dimensions use the same unit before calculating the volume.
If you are working on a project with several shapes or section, total the sum of the areas. This way will be far more precise than imagining anirregular project asa gigantic rectangle.
That would be determined by the slab’s thickness. 10 x 10 does come to a square of 100’ but you need to know that other measurement ( thickness) in order to get to the volume.
Calculate in cubic feet by (length x width x thickness) where all three values are already calculated in feet. Then take the result from step 1 and divide by 27 (number of cubic feet in a cubic yard).
There are 27 cubic feet in one cubic yard. To convert to yards, cubiit feet, there are cubic feet? 3/27 in one yard.
For a cylindrical footing use the radius height. Half the diameter to give the radius. Please ensure all dimensions are using a consistent unit.
The mathematical result the calculated volume is just the measured volume. Where actual ordering is involved, allowance has to be made for spillage, waste, uneven excavation and the variability of measurements. The amount of allowance suitable for each project.
There are several volume calculators that can provide a concrete quantity estimate. In order to obtain material costs we need to know the supplier's current per unit cost, delivery fees, minimum load size or any job related costs.
Measure each section separately, add the sections and calculate before adding waste. Compare the result with the exact package coverage and round up to a purchasable quantity.
As a quick reference, the table below has the estimated quantity of concrete to provide a 10-foot by 10-foot rectangular slab at different thicknesses; this doesn’t factor in waste, imperfect excavations, and so on.
| Slab Size | Thickness | Volume (Cubic Feet) | Volume (Cubic Yards) |
|---|---|---|---|
| 10 ft × 10 ft | 3 inches | 25.00 | 0.93 |
| 10 ft × 10 ft | 4 inches | 33.33 | 1.23 |
| 10 ft × 10 ft | 5 inches | 41.67 | 1.54 |
| 10 ft × 10 ft | 6 inches | 50.00 | 1.85 |
| 10 ft × 10 ft | 8 inches | 66.67 | 2.47 |
Concrete quantities are often discussed in cubic feet and cubic yards. Keeping the conversion relationship clear helps prevent ordering mistakes.
Assuming a straight, rectangular sidewalk, determine the total length, mean width and desired thickness. If the width of the sidewalk varies or the depth changes, break the sidewalk up into sections and determine each section separately.
For example, a sidewalk measuring 30 feet long, 4 feet wide, and 4 inches thick has an approximate volume of:
30 × 4 × (4 ÷ 12) = 40 cubic feet
Converting to cubic yards:
40 ÷ 27 = approximately 1.48 cubic yards
This is the theoretical volume before considering project-specific allowances.
For rectangular patio follow the same volume as a slab. Use finished dimensions instead of estimating from yard area.
Use separate calculations for any sections of the patio which has steps; or different depths; or footing or any other component with dimensions dissimilar. Calculate a more precise aggregate with summation.
There are various forms and sizes for footings depending on the project. For a rectangular one the calculation would be length width depth, and for a round one we would need to do a cylindrical volume calculation.
For footing use as a structural component or any form of load bearing; the calculator is intended only for quantity take off material estimation purposes. The design will have the necessary dimensions; reinforcment and or detailing to specifications in accordance with the appropriate designs, codes, manufacturer,s specifications or under supervision of a competent professional.
Whether the ready-mix was delivered via a ready-mix truck or was bought in bags doesn’t matter. As far as volume is concerned. What does matter is that you ordered it the right way, right?
Ready mix should be measured by volume when ordered. bagged products are ordered by the manufacturers described yield after the batch is mixed. You cant assume, for instance, that a six inch will take X number of bags. Use the products yield on the package.
The concrete volume is proportional to the dimensions entered in the calculation. Therefore, if the length, the width or the thickness measured are wrong, the estimated quantity will also be wrong.
It's also important to pay special attention to depth because small variations within the big slab may be significant from a total volume perspective. Be sure to measure any variation in depth throughout the same project individually and do not use an average depth unless this accurately reflects how the work will be performed.