Concrete estimating
Use this concrete calculator to estimate how much concrete you need for slabs, walls, footings, columns, round slabs, tubes, curbs, gutters, and stairs. Enter your measurements, choose your units, and this free concrete calculator will estimate concrete volume in cubic feet, cubic yards, and cubic meters, along with concrete weight and the number of 60 lb or 80 lb concrete bags. Whether you are planning a driveway, patio, fence post, or staircase, this online concrete calculator helps you get accurate concrete estimates before ordering ready-mix concrete or buying bagged concrete.
Concrete estimate result
Enter dimensions above, then calculate your estimate.
-- cubic feet
or -- cubic yards
or -- cubic meters
If using pre-mixed concrete with density of 2,130 kg/m3 or 133 lbs/ft3*:
* Different types of concrete can have very different densities.
How to use
To use this concrete calculator, first choose the shape that matches your project. A slab, wall, or square footing needs length, width, and thickness or height. A column or post hole needs diameter and depth. A round slab or concrete tube uses outside diameter, inside diameter when needed, and height or thickness. Curbs, gutters, and stairs use their own dedicated measurements.
After entering the measurements, choose the unit system that matches your project. The concrete calculator supports feet, inches, yards, meters, and centimeters, then converts the result into concrete volume, concrete weight, and concrete bags.
Measurements
Concrete volume measurements help you communicate with suppliers and plan your order. This concrete calculator displays results in cubic feet, cubic yards, and cubic meters so you can use whichever unit your project requires. In the United States, ready-mix concrete suppliers typically price and deliver by the cubic yard. For smaller DIY concrete projects, cubic feet and concrete bags are often more practical units.
A cubic yard of concrete equals 27 cubic feet. When you calculate concrete volume and see the cubic yards result, that number tells you how many full cubic yard units to order from a ready-mix supplier. A standard concrete truck delivers 8 to 10 cubic yards per load, so knowing your total cubic yards helps you plan delivery logistics and avoid multiple small orders.
To convert cubic feet to cubic yards, divide the cubic feet value by 27. For example, if your concrete calculator shows 54 cubic feet, that equals 2 cubic yards. This conversion matters when ordering ready-mix concrete because suppliers quote prices per cubic yard and may charge extra for small loads under their minimum order.
Cubic meters are the metric equivalent for measuring concrete volume. One cubic meter equals 35.3 cubic feet. Many countries outside the United States order concrete by the cubic meter, and this concrete calculator shows both cubic feet and cubic meters so you can work with either measurement system.
Weight & bags
Concrete weight estimation helps you plan handling, transport, and delivery for your project. This concrete calculator estimates concrete weight in pounds and kilograms from the calculated concrete volume. Normal-weight concrete typically weighs about 133 to 150 pounds per cubic foot, or approximately 2,130 kilograms per cubic meter, depending on the mix design and aggregate.
For bagged concrete projects, the concrete bag calculator converts your volume estimate into a practical bag count. Bagged concrete comes in common sizes including 60 lb bags and 80 lb bags. Each bag covers roughly 0.45 to 0.6 cubic feet depending on the product. The concrete calculator rounds up the bag count to ensure you order enough material and do not run short during your pour.
Shapes
Pick the shape that matches the way the concrete will be formed. If your project combines shapes, calculate each part separately and add the results together. This helps the Concrete Calculator work as a complete concrete slab calculator, concrete wall calculator, concrete footing calculator, concrete column calculator, round slab concrete calculator, concrete tube calculator, curb and gutter concrete calculator, and concrete stairs calculator from one page.
The concrete slab calculator is designed for flat or rectangular concrete projects such as driveways, patios, garage floors, shed pads, sidewalks, pads, and simple rectangular pours. Enter the length, width, thickness, and quantity, and the Concrete Calculator estimates concrete volume in cubic feet, cubic yards, and cubic meters. Thickness is one of the most important inputs for a slab because a small change from 4 inches to 5 inches can noticeably increase the amount of concrete needed. Use this concrete slab calculator before ordering ready-mix concrete or buying concrete bags so your estimate includes the full slab area and a practical allowance for waste.
The same rectangular concrete calculator can also work as a concrete wall calculator or square footing calculator. For walls, enter the wall length, wall height, wall thickness, and number of wall sections. For square footings, rectangular foundations, and structural pads, enter length, width, depth, and quantity. Wall and footing projects often need careful estimating because small measurement errors can affect concrete volume, concrete weight, and concrete bag count. This section is useful for retaining walls, garden walls, foundation sections, small building bases, and straight concrete footings.
The concrete column calculator estimates concrete for round footings, fence post holes, deck posts, pier foundations, cylindrical forms, and repeated round holes. Enter the diameter, depth or height, and quantity, and the Concrete Calculator calculates total concrete volume for one or many columns. This is especially useful when you need a post hole concrete calculator for a fence line or deck layout, because the quantity field helps multiply the same diameter and depth across the entire project. For tube forms and round form projects, use the diameter and height fields to estimate the concrete required for each cylindrical form.
The round slab concrete calculator is made for circular pads, round patios, round platforms, fire pit bases, circular shed bases, and other round concrete projects. Instead of entering length and width, you enter the outside diameter, thickness or height, and quantity. A round slab calculator is helpful when a rectangular slab calculator does not match the project shape. Circular projects can be harder to estimate by hand because the volume depends on radius. By entering diameter and thickness, you can estimate cubic feet, cubic yards, cubic meters, concrete weight, and concrete bags for a round slab.
The concrete tube calculator is for tube-shaped or hollow cylinder projects where the center is not filled with concrete. Enter outside diameter, inside diameter, length or height, and quantity. This concrete calculator subtracts the inner empty space from the outer cylinder to estimate only the concrete volume required for the ring-shaped section. Use it for hollow columns, circular walls, pipe-like forms, sleeves, and round structures where a standard round slab concrete calculator would overestimate material by filling the center.
The curb and gutter concrete calculator estimates concrete for sidewalk edges, road curbs, driveway edges, drainage channels, gutter sections, and combined curb barriers. This calculator uses curb depth, gutter width, curb height, flag thickness, length, and quantity to estimate the concrete needed for a curb and gutter section. Curb and gutter projects are more complex than a simple slab because the shape includes multiple dimensions. A dedicated curb and gutter concrete calculator helps avoid underestimating material when the project includes both a raised curb and a flat gutter panel.
The concrete stairs calculator estimates concrete for steps, stair entrances, porch steps, and small stair projects. Enter the tread depth, riser height, stair width, platform depth, number of steps, and quantity. The Concrete Calculator estimates the volume for the stair shape and includes the result in cubic feet, cubic yards, cubic meters, weight, and bag count. Concrete stairs are harder to estimate than a flat slab because each step adds a different section of volume. A concrete stairs calculator turns tread, riser, width, landing depth, and step count into a practical concrete estimate before construction begins.
Results
The result area converts the same estimate into concrete volume, concrete weight, and concrete bag counts so you can compare ready-mix and bagged concrete options. The goal is to answer both "how much concrete do I need" and "how many bags of concrete do I need" from the same measurements.
The concrete calculator shows concrete volume in cubic feet, cubic yards, and cubic meters so you can use the result for different ordering methods. In the United States, ready-mix concrete is commonly ordered by cubic yard, while smaller projects may be planned in cubic feet or converted into concrete bags. Metric projects can use cubic meters.
The concrete weight calculator estimate helps you understand how heavy the calculated concrete volume will be. This can be useful for transport, delivery, handling, and planning around site access. The Concrete Calculator shows estimated weight in pounds and kilograms using a normal-weight concrete density assumption.
For bagged concrete projects, the concrete bag calculator estimates how many 60 lb bags or 80 lb bags are needed. This is useful for small slabs, post holes, steps, fence posts, and DIY repairs where buying ready-mix concrete by truck may not be necessary. Bag counts are rounded up after the selected waste allowance is included.
Reference
Each formula is calculated after converting every dimension to feet, then converted into cubic yards and cubic meters for ordering. These formulas are why a concrete volume calculator needs the correct shape: a slab, cylinder, hollow cylinder, curb, and stair do not use the same geometry. Understanding these formulas helps you verify that your concrete calculator result matches your manual estimates.
Volume = length × width × thickness × quantity. The slab concrete calculator uses this rectangular formula for driveways, patios, pads, floors, walls, and square footings after all measurements are converted to the same unit. This concrete slab calculator formula works for any flat rectangular project where you know the surface area and depth.
Volume = π × radius² × height × quantity. The concrete column calculator and round slab concrete calculator use this formula after converting diameter into radius. This formula is essential for post holes, round footings, and circular pads where the concrete estimator must account for the circular cross-section.
Volume = π × (outer radius² - inner radius²) × height × quantity. The concrete tube calculator subtracts the inner cylinder so only the ring-shaped concrete volume is counted. This concrete calculator formula is useful for sonotube forms, hollow columns, and pipe-like structures where the center remains empty.
Volume = (width × run × rise × steps × (steps + 1) ÷ 2) + (width × platform depth × (steps + 1)) × quantity. The concrete stairs calculator estimates the combined volume of the stepped section and landing. This concrete calculator formula accounts for the triangular volume under each step and the flat landing at the top.
Volume = length × ((curb depth × curb height) + (gutter width × flag thickness)) × quantity. This formula combines the raised curb and the gutter flag into one curb and gutter concrete calculator result. The concrete calculator for curbs handles the L-shaped cross-section where the curb rises above the gutter panel.
Weight = volume × density. Bags = order weight ÷ bag size, rounded up. The concrete bag calculator uses the waste-adjusted estimate so 60 lb bags and 80 lb bags are not undercounted. This concrete estimator converts cubic feet to bag counts by first calculating total concrete weight, then dividing by the bag size and rounding up to the nearest full bag.
Ordering guide
The amount of concrete you need depends on the shape, dimensions, thickness, and quantity of your project. A Concrete Calculator estimates this by converting your measurements into concrete volume. For most larger projects, the most useful number is cubic yards because ready-mix concrete is usually ordered by the cubic yard. For small DIY projects, the concrete bag calculator result may be more practical.
Measure the actual formed space whenever possible. Excavated post holes, rough subgrades, and handmade forms are rarely perfect, so the measured space may differ from the plan. A waste allowance helps cover uneven ground, form movement, spillage, and small measurement errors.
A waste allowance compensates for material lost during placement, spreading, and finishing. Even experienced contractors typically add 5% to 10% extra concrete when ordering ready-mix concrete. For complex shapes like stairs, curbs, and tubes, waste can be higher, so aim toward 10%. For simple flat slabs on level ground, 5% may be sufficient. The waste allowance in this concrete calculator is adjustable so you can match your project's complexity and your comfort level with estimating risk.
Ordering guide
Choosing between ready-mix concrete and bagged concrete depends on your project size, site access, and timeline. This section helps you decide which ordering method works best for your concrete project.
Order ready-mix concrete when your project needs more than 2 to 3 cubic yards, or when you need consistent quality across a large pour. Ready-mix concrete is delivered by truck and placed directly into your forms, which saves significant labor compared to mixing bags on-site. Ready-mix suppliers price concrete by the cubic yard and typically have minimum orders of 1 to 3 cubic yards. Use this concrete calculator to estimate your total cubic yards before calling a ready-mix supplier.
Bagged concrete works well for small projects like fence post holes, small slabs, steps, repairs, and footings under 2 cubic yards. Bagged concrete comes in 60 lb bags and 80 lb bags that you mix with water. The concrete bag calculator helps you estimate how many bags to buy so you do not make multiple trips to the hardware store. Bagged concrete is also useful when site access prevents a concrete truck from reaching the pour location.
FAQ
The amount of concrete you need depends on the shape, dimensions, thickness, and quantity of the project. A concrete calculator estimates this by converting your measurements into concrete volume. For a slab, wall, or footing, the key inputs are length, width, and thickness. For a post hole or column, the key inputs are diameter and depth. Most projects should also include a waste allowance before ordering.
The number of concrete bags depends on the concrete volume, the bag size, and the product yield. This concrete calculator estimates 60 lb bags and 80 lb bags by converting the project volume into an estimated weight and rounding up. Bag yield can vary by brand and mix type, so the final purchase should always be checked against the yield printed on the bag.
To find how many cubic yards of concrete you need, calculate the total cubic feet and divide by 27. This concrete calculator displays cubic yards directly so you can order ready-mix concrete by the cubic yard. For example, a 10-foot by 10-foot slab at 4 inches thick equals about 1.23 cubic yards. Always round up when ordering.
To calculate concrete for a slab, multiply length by width by thickness, then multiply by quantity. The concrete slab calculator converts those measurements into cubic feet, cubic yards, and cubic meters. Because slab thickness has a large effect on concrete volume, measure or confirm the planned thickness before ordering ready-mix concrete or buying concrete bags.
To calculate concrete for a round slab, enter the diameter and thickness of the slab. The round slab concrete calculator converts diameter into radius and uses the circular volume formula to estimate cubic feet, cubic yards, cubic meters, concrete weight, and concrete bags. This is better than using a rectangular slab calculator for circular patios, round bases, and fire pit pads.
Use the concrete column calculator for post holes, round footings, fence posts, deck posts, and pier foundations. Enter the hole diameter, depth, and quantity. The calculator estimates the total concrete volume for all holes, then converts that result into concrete weight and bag count. This is useful when many posts share the same diameter and depth.
There are 27 cubic feet in one cubic yard of concrete. Ready-mix concrete is commonly ordered by the cubic yard in the United States, so a concrete volume calculator often shows both cubic feet and cubic yards. Cubic feet can be easier for small measurements, while cubic yards are usually more useful when talking to a ready-mix supplier.
An 80 lb bag of concrete yields approximately 0.6 cubic feet, or about 0.022 cubic yards. One cubic yard equals roughly 45 bags of 80 lb concrete. The concrete bag calculator rounds up to the nearest full bag, so you do not under-order when purchasing bagged concrete for your project.
Yes. Most concrete projects should include extra material for waste, uneven ground, form variation, spillage, and measurement errors. Many users add 5% to 10% extra concrete before ordering. The concrete calculator gives a geometric estimate, but a small waste allowance helps prevent running short during the pour.
Concrete slab thickness depends on the project, load, subgrade, reinforcement, and local requirements. Many residential patios and walkways use a different thickness than driveways, garage floors, or structural slabs. This concrete calculator can estimate volume for any thickness you enter, but structural thickness should be chosen from project plans, local code, or a qualified professional.
Yes. The concrete weight calculator result estimates weight in pounds and kilograms from the calculated concrete volume. Normal-weight concrete is often estimated around 133 to 150 pounds per cubic foot, or about 2,130 kilograms per cubic meter. Actual weight can vary based on the mix design, aggregate, moisture, reinforcement, and supplier.
Yes. The concrete bag calculator estimates common 60 lb bags and 80 lb bags from the waste-adjusted concrete estimate. This is useful for small slabs, post holes, stair repairs, fence posts, and other projects where bagged concrete is easier than ready-mix delivery. Always compare the calculator result with the bag yield listed by the manufacturer.
The number of bags for a 4-foot pier depends on the pier diameter and the bag size. Use the concrete column calculator, enter the hole diameter as 4 feet (or your actual diameter), enter the depth as 4 feet, and the calculator estimates total concrete volume, weight, and bag count for one or multiple piers.