More costs and pricingPumping, labor and finishing, delivery and other fees
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Multiply length × width × thickness in feet to get cubic feet, then divide by 27 for cubic yards. A 10 × 10 ft slab 4 inches thick takes about 1.23 cubic yards, which is 56 bags of 80 lb mix, since each 80 lb bag yields 0.60 cubic feet and 45 of them make a yard. Order 5 to 10% extra for waste, and expect ready mix to run about $160 to $195 a yard.
How to calculate concrete in cubic yards
Every shape comes down to cubic feet divided by 27. This concrete yard calculator picks the formula for your shape and adds your waste.
| What to measure enter these in the calculator | Volume in cubic feet all sizes in feet | |
|---|---|---|
| Slab, footing or wall | Length, width, and thickness or depth | Length × Width × Thickness (inches ÷ 12) |
| Round column | Diameter and height | 3.1416 × (Diameter ÷ 2)² × Height |
| Circular tube | Outer and inner diameter, height | 3.1416 × [(Outer ÷ 2)² minus (Inner ÷ 2)²] × Height |
| Steps | Platform depth, rise, run, width, steps | Depth × Width × Total rise, plus Run × Rise × Width × Steps × (Steps minus 1) ÷ 2 |
| Curb and gutter | Curb depth and height, gutter width, flag thickness, length | Length × [Flag thickness × (Gutter width + Curb depth) + Curb height × Curb depth] |
| Cubic yards | Quantity and waste allowance | Cubic feet × Quantity × (1 + waste %) ÷ 27 |
| Total cost | Price per cubic yard, or per bag | Cubic yards × Price per yard, or bags × Price per bag |
Worked example: a 20 × 10 ft slab, 6 inches thick, with 10% waste
When to use this concrete calculator
Any time a pour is coming up, from a single post hole to a new build, a renovation or a landscaping job, run the numbers first so the order matches the forms.
- Before ordering materials: confirm the exact yardage before you call the plant.
- Project planning: a driveway or garage floor needs a delivery date, a truck count and a budget long before the forms go in. Work out the yards here, see how many trucks that fills, and price it on the second tab so the schedule and the money line up.
- Odd shapes: round columns, tubes, steps and curbs all convert to cubic yards.
- Budgeting: compare how a thicker slab or a lighter mix changes the total. Going from 4 to 6 inches adds half again to the concrete, and the weight figure shows what the base has to carry.
- Cutting waste: set just enough overage for leveling and finishing.
- Bags or a truck: check whether a small job is cheaper in 80 lb bags than a part load with a short load fee on top.
- Bidding a job: concrete contractors can use this concrete yard calculator to check yardage on a bid. Then price the pour with their own yard price, reinforcement, labor per square foot and profit margin, so the quote and the order come from the same numbers.
How this concrete calculator works
Pick a shape and your units, then enter lengths in feet and depths in inches (or meters and centimeters), the way you would read them off a tape on site. The tool converts everything to cubic feet, multiplies by the quantity, adds the waste allowance and shows cubic yards, cubic feet, cubic meters, 40, 60 and 80 lb bag counts, weight in pounds and tons, the order rounded up to the next half yard and how many trucks that fills. One cubic yard is 0.7646 cubic meters, and the Price the pour tab turns the yards into a cost, so 4.07 yards at about $180 a yard comes to roughly $733.
How many bags of concrete do you need?
An 80 lb bag of premixed concrete yields about 0.60 cubic feet, so 45 bags make one cubic yard. Smaller bags yield less, and the count climbs fast.
| Bag size | Yield per bag | Bags per cubic yard | Bags for a 10 × 10 ft slab, 4 in |
|---|---|---|---|
| 80 lb | 0.60 cu ft | 45 | 56 |
| 60 lb | 0.45 cu ft | 60 | 75 |
| 40 lb | 0.30 cu ft | 90 | 112 |
Bag counts are rounded up to whole bags and leave out waste. Add your overage before you buy.
How much concrete do common slab sizes need?
A cubic yard covers about 81 square feet at 4 inches thick. Here is the net volume for the slab sizes people pour most, before waste.
| Slab size | 4 in thick | 5 in thick | 6 in thick | 80 lb bags at 4 in |
|---|---|---|---|---|
| 10 × 10 ft | 1.23 cu yd | 1.54 cu yd | 1.85 cu yd | 56 |
| 12 × 12 ft | 1.78 cu yd | 2.22 cu yd | 2.67 cu yd | 80 |
| 10 × 20 ft | 2.47 cu yd | 3.09 cu yd | 3.70 cu yd | 112 |
| 20 × 20 ft | 4.94 cu yd | 6.17 cu yd | 7.41 cu yd | 223 |
| 24 × 24 ft | 7.11 cu yd | 8.89 cu yd | 10.67 cu yd | 320 |
| 30 × 30 ft | 11.11 cu yd | 13.89 cu yd | 16.67 cu yd | 500 |
Past about 10 yards you are into a second truck, since a standard mixer carries 8 to 10 cubic yards.
How thick should a concrete slab be?
For most home slabs, 4 inches is the standard. Anything that carries a car or truck needs more.
| Project | Typical thickness | 80 lb bags per 100 sq ft |
|---|---|---|
| Patios, walkways, garden sheds, most house floors | 4 in | 56 |
| Driveways and anything that carries cars | 5 to 6 in | 70 to 84 |
| Heavy vehicles, RV pads, shop floors | 6 in or more, usually reinforced | 84 or more |
Wire mesh, rebar, plastic mesh and fiber are all used to reinforce slabs, and a standard home rebar grid uses #3 or #4 bar every 12 to 18 inches. Plan control joints too: cut them at least a quarter of the slab thickness deep, and space them no more than 2.5 feet per inch of thickness, so 10 feet apart on a 4 inch slab. Tighter is better, and the calculator suggests a spacing for any slab you enter.
How much does concrete cost per yard?
Ready mix runs about $160 to $195 a cubic yard across the US, and averaged close to $180 in 2025. The extras below are what turn a yard price into the real bill.
| Item | Typical price | When it applies |
|---|---|---|
| Ready mix concrete | $160 to $195 per cu yd | Every truck order |
| Premixed bags | $4.50 to $27 per bag | Price depends on the mix, from basic to fast setting and high strength |
| Short load fee | $40 to $60 per cu yd | Part loads that do not fill the truck |
| Pumping | $2 to $10 per cu yd | Where the truck cannot reach the forms; renting a tow behind pump adds $150 to $200 an hour |
| Weekend, holiday or winter delivery | About $8 per cu yd | Off day pours and cold weather mixes |
| Long haul delivery | About $9.50 per mile | Sites more than 20 miles from the plant |
| Wire mesh | $0.35 per sq ft | Patios, walks and light slabs |
| Rebar grid | $2 to $3 per sq ft | Driveways, heavy loads, weak soil |
| Plain slab, poured and finished | $6.50 to $10.50 per sq ft | Hiring a contractor for the whole job |
So 100 cubic feet of concrete, which is 3.70 yards, costs about $593 to $722 in ready mix alone.
What changes how much concrete you need?
The formula gives the volume of a perfect form on perfectly flat ground. Real sites add a little, and these are the usual reasons.
| Factor | What changes | Typical effect |
|---|---|---|
| Thickness | The biggest lever on any slab. | 4 to 6 inches adds 50% more concrete |
| Ground conditions | Clean forms on firm, level ground lose very little. Rough ground, soft spots and hand dug footings swallow concrete you never see again. | 5 to 10% extra on clean pours, 10 to 15% on rough ground |
| Shape | Curves, steps and irregular outlines are harder to measure, and over digging is common. | Toward the top of the waste range |
| Spills and finishing | Some concrete stays in the chute, the mixer and the wheelbarrow, and leveling takes a little more. | Covered by the waste allowance |
| Order rounding | Plants batch in steps, so it is safer to round up than to come up short mid pour. | Round up to the next half yard |
| Truck size | A standard mixer carries 8 to 10 cubic yards. | Bigger pours need a second truck |
| Mix type | Lightweight mixes change the weight, not the volume, which matters for elevated slabs and what the base has to carry. | 90 to 115 lb per cu ft lightweight, 140 to 150 normal |
How do concrete contractors estimate a pour?
Yardage first, price second. A bid built on a sloppy volume either loses money on the pour or loses the job to a sharper number.
- Measure the siteTake length, width and depth at several points, not just the corners. The low spots in the subgrade are where the extra concrete goes.
- Work out the volumeCubic feet divided by 27 gives cubic yards.
- Add waste and round upAdd 5 to 10%, more on rough ground or hand dug footings. Then round the order up to the next half yard so the plant, not the truck, sets the end of the pour.
- Price the concreteSupplier yard price, plus any short load, pumping or weekend fee.
- Add reinforcement and laborMesh or rebar by the square foot, then labor and finishing by the square foot.
- Set your margin and send itShow concrete, reinforcement and labor as separate lines. A homeowner holding three driveway bids trusts the one they can read.
The Price the pour tab runs exactly this math from the yards you worked out on the first tab.
Concrete contractors: the next driveway quote calls while your hands are in wet concrete.
Nobody stops floating a slab to answer the phone, so pour days are exactly when new leads hit voicemail and ring the next number in the search results instead. ServiceAgent picks up each one, asks for the size and the timeline, books the site visit into your calendar and follows up with the customer.
Book a free demoFrequently asked questions
Short answers on yards, bags, weight, waste and what a pour costs.
Book a free demoHow do I calculate how much concrete I need?
Multiply length by width by thickness, all in feet, to get cubic feet. Divide by 27 to turn that into cubic yards, then add 5 to 10 percent for waste. A slab 20 feet by 10 feet and 6 inches thick is 100 cubic feet, or 3.70 cubic yards, and about 4.07 yards once you add 10 percent.
How many bags of concrete make a cubic yard?
It takes 45 bags of 80 lb mix, 60 bags of 60 lb mix or 90 bags of 40 lb mix. An 80 lb bag yields about 0.60 cubic feet, a 60 lb bag 0.45 and a 40 lb bag 0.30.
How accurate is this concrete yard calculator?
The volume math is exact for the sizes you enter. A real pour usually needs a little more, because ground is rarely flat, forms bow slightly and some concrete stays in the mixer and the wheelbarrow. That is what the waste allowance covers, and why it pays to round your order up rather than down.
Should I order extra concrete?
Yes. Plan on 5 to 10 percent extra for clean forms on firm, level ground, and 10 to 15 percent for rough ground, hand dug footings or odd shapes. Running short halfway through means a second delivery and a visible seam where the two pours meet.
How much does 100 cubic feet of concrete cost?
100 cubic feet is 3.70 cubic yards. At ready mix prices of about $160 to $195 a yard, the concrete alone comes to roughly $593 to $722, before delivery extras, pumping or labor. A part load that small may also carry a short load fee of $40 to $60 a yard.
What affects the cost of concrete the most?
Volume comes first, and that is set by the slab size and thickness. After that it is the mix you order, short load and delivery fees, pumping, reinforcement and what suppliers charge in your area.
Can I enter my own price per cubic yard?
Yes. Open the Price the pour tab and type your supplier's price per yard, or switch to bags and enter the shelf price per bag. The total updates as you type.
Should I use bags or ready mix concrete?
Bags suit small jobs under about one cubic yard, like post holes, an equipment pad or a single step. Driveways and big slabs are easier to order by the yard, because mixing dozens of bags by hand is slow and hard to keep consistent.
How much does a cubic yard of concrete weigh?
About 4,000 pounds, or two US tons. Normal weight concrete runs about 140 to 150 pounds per cubic foot, while structural lightweight concrete is about 90 to 115.
Is this calculator useful for concrete contractors?
Yes. Contractors use it to check yardage on a bid and to price the pour with their own yard price, reinforcement, labor per square foot and margin. ServiceAgent then answers the calls those bids come from and books the site visits, so quotes and leads sit in one workflow.
Leads growth and product marketing for ServiceAgent at SaaS Labs, where he has worked in product marketing since 2020. Writes ServiceAgent's coverage of AI call answering, CRM and home services operations.
Published by ServiceAgent, the AI front office for home service teams. Estimates only. Actual quantities and prices depend on your site, your forms, the mix you order and your local supplier. Check measurements on site and confirm with your supplier before you order.