How to Estimate Concrete for Any Project
Estimating concrete comes down to two numbers: how much you need, and what it will cost. Get the volume right and everything else follows. Get it wrong and you either run short mid-pour or pay for a truck you didn't need.
Here is the method the pros use, and the same math our calculators run for you.
The five-step estimate
- Measure the space in feet. For a flat pour like a slab, patio, or driveway, you need length, width, and thickness. Thickness is almost always in inches, so a 4 inch slab is 4 divided by 12, or 0.333 feet.
- Find the volume in cubic feet. Multiply length by width by thickness in feet. A 20 by 20 patio at 4 inches is 20 x 20 x 0.333, which is 133.3 cubic feet.
- Convert to cubic yards. Concrete is ordered by the cubic yard, and one cubic yard is 27 cubic feet. So 133.3 divided by 27 is 4.94 cubic yards.
- Add waste. Spillage, uneven subgrade, and slab edges eat into every pour. Add 5 to 10 percent. That 4.94 becomes about 5.2 to 5.4 yards, so you order 5.5.
- Turn it into a cost. Multiply your yards by the delivered price per cubic yard, then add labor, delivery, and any short-load fee if you are under the truck minimum.
If you would rather skip the arithmetic, the concrete cost estimator does all five steps and gives you yards, bags, and a dollar figure at once.
Ordering ready-mix vs mixing bags
Under about a cubic yard, hand-mixing bags usually wins. Over a yard, a ready-mix truck is faster and cheaper per yard. A quick rule for bags: an 80 lb bag yields about 0.6 cubic feet, so it takes roughly 45 of them to make one cubic yard. The concrete cost estimator shows both the truck price and the bag count side by side so you can see where the line is for your job.
Estimate vs quote
An estimate is your own working number, useful for ordering material and sanity-checking a bid. A quote is a contractor's firm price for the finished job, which includes forming, reinforcement, finishing, and cleanup. Use the estimate to know roughly what a project should run, then compare it against the quotes you get. If a quote is miles off your estimate, ask what is driving the difference.
Where to go next
- How much does concrete cost? for current per-yard and per-project prices.
- Concrete cost per square foot when you already know your area.
- How to estimate concrete for a slab with a full worked example.
- Concrete patio cost for a common weekend project.
- A free concrete estimate template you can print or edit.
- Best concrete estimating software if you bid jobs for a living.
Not sure how many yards you need first? Start with how much concrete do I need, then come back to price it.
Explore the concrete estimate guides
Work through the guides below, from a full cost breakdown to a printable estimate template.
- How Much Does Concrete Cost?What concrete costs in 2026: price per cubic yard, per square foot, delivery and short-load fees, and what drives the number. Real ranges and a free estimator.
- Concrete Cost Per Square FootWhat concrete costs per square foot in 2026 by thickness and finish, how to convert square feet to cubic yards, and a fast way to price your slab.
- How to Estimate a SlabEstimate concrete for a slab step by step. Measure, convert to cubic yards, add waste, and get a bag count, with a full worked example and a free calculator.
- Concrete Patio CostConcrete patio cost in 2026 by size and finish, from plain to stamped. See per square foot prices, what drives them, and how to price your own patio.
- Concrete Estimate TemplateA free concrete estimate template you can print or edit. Line items for material, labor, delivery, and waste, plus how to fill it in and price a job.
- Concrete Estimating SoftwareA plain guide to concrete estimating software in 2026: takeoff tools, full estimating suites, what to look for, and when a free calculator is enough.
Sources
Frequently asked questions
How do you estimate concrete for a job?
Measure length, width, and thickness in feet, multiply them for cubic feet, divide by 27 for cubic yards, then add 5 to 10 percent for waste. Multiply the result by the delivered price per yard to get a material cost.
How much extra concrete should I order for waste?
Add 5 percent on flat, well-formed slabs and up to 10 percent on rough subgrade or small pours where a partial bag or a short load hurts more. It is cheaper to have a little left over than to stop a pour halfway.
How many 80 lb bags make a cubic yard?
About 45. Each 80 lb bag yields roughly 0.6 cubic feet, and a cubic yard is 27 cubic feet.
Is it cheaper to mix my own concrete or order a truck?
For small jobs under about a cubic yard, bags are usually cheaper and there is no delivery fee or truck minimum. Once you pass a yard or so, ready-mix costs less per yard and saves hours of mixing.