Concrete Calculator
Find out how many cubic yards of concrete you need and estimate the cost.
How do you calculate how much concrete you need?
Concrete volume is calculated by multiplying length x width x thickness, all converted to the same unit. Since slab thickness is usually measured in inches while length and width are in feet, this calculator converts thickness to feet first, then divides the resulting cubic feet by 27 to get cubic yards — the unit ready-mix concrete is typically sold in. Most residential slabs, patios, and sidewalks use a 4-inch thickness, while driveways and areas that will see vehicle weight often call for 5-6 inches.
Should I order ready-mix or mix bags myself?
For anything larger than a small patch, ordering ready-mix concrete delivered by truck is almost always more cost-effective and less labor-intensive than mixing dozens of 80lb bags by hand. This calculator shows both the cubic yard figure for ordering ready-mix and the equivalent number of 80lb bags in case you're tackling a small DIY project like a fence post footing or a short walkway section.
These figures are estimates for planning purposes — always round up slightly when ordering, since running short mid-pour is far more costly than having a bit extra, and actual pricing varies by region, supplier, and delivery fees.
Frequently Asked Questions
How many 80lb bags of concrete equal one cubic yard?
An 80lb bag yields roughly 0.6 cubic feet of concrete, so it takes about 45 bags to make one cubic yard (27 cubic feet). For anything beyond a small patch, ready-mix delivery is usually faster and cheaper than buying and mixing that many bags.
How thick should a concrete slab be?
Standard residential slabs like patios and sidewalks are typically poured 4 inches thick, while driveways and areas supporting vehicle weight are usually 5-6 inches to handle the extra load without cracking.
Why is concrete sold in cubic yards instead of cubic feet?
Ready-mix concrete trucks measure and price their loads in cubic yards because it's a more practical unit for the large volumes involved in construction. One cubic yard equals 27 cubic feet, which is why this calculator converts your slab's cubic footage before showing the final order quantity.
Should I order extra concrete beyond the calculated amount?
Yes — most contractors add 5-10% extra to account for uneven subgrade, spillage, and form imperfections. Running short mid-pour can cause a visible seam or cold joint, so it's safer to round up slightly when placing your order.
How much does a cubic yard of concrete cost?
Ready-mix concrete typically costs $110-$165 per cubic yard depending on region and mix strength, plus potential delivery minimums or short-load fees if your order is small. Enter your local quoted price above for a more accurate total.
Is it cheaper to mix concrete myself or order ready-mix?
For small jobs under half a cubic yard, bagged concrete mixed by hand is often more practical. For anything larger, ready-mix delivery is typically cheaper per cubic yard and saves significant labor and time compared to mixing dozens of bags.
Does this calculator account for rebar or wire mesh reinforcement?
No, this tool estimates concrete volume and cost only. Reinforcement materials like rebar or wire mesh are priced separately and depend on local building codes and the specific load requirements of your project.
How accurate is this concrete estimate?
This calculator gives a solid planning-stage estimate based on your entered dimensions and cost per cubic yard, but actual supplier pricing, delivery fees, and minimum order requirements vary by region and contractor.