Construction · Materials
Concrete CalculatorCalculate cubic yards for slabs, driveways, footings, and pours.
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Example — 12 × 10 ft driveway
1.48
cubic yards
A standard 4-inch driveway at 12 × 10 ft needs about 1.5 cubic yards — roughly 90 bags. Always order 10% extra to allow for spillage and waste.
Concrete Calculator & Tools Hub
Calculate concrete volume, estimate materials, and plan costs — all in one place.
Use this concrete calculator to estimate how many cubic yards of concrete you need for slabs, driveways, patios, and footings. Enter your dimensions to quickly calculate volume, number of bags, and rough cost.
How much concrete do I need?
Concrete is measured and sold in cubic yards in the US. One cubic yard equals 27 cubic feet — roughly a 3 ft × 3 ft × 3 ft cube. To find your number, you multiply the length, width, and thickness of your pour, then divide by 27.
Thickness has a big impact. A standard 4-inch slab and a 6-inch slab of the same footprint require 50% more concrete. Always confirm your thickness requirement before calculating — driveways typically need 4–6 inches, patios 3–4 inches, and footings vary by structural load.
For small pours under 1 cubic yard, bagged concrete (Quikrete, Sakrete) is the practical choice. For anything larger — driveways, garage floors, foundations — ordering ready-mix by the yard is faster, more consistent, and usually cheaper per cubic yard.
Concrete Volume Calculators
Work out how much concrete you need — in cubic yards, cubic feet, or bags.
Concrete Slab Calculator
Calculate volume for slabs, driveways, patios, and garage floors.
Calculate volume →Concrete Cost Calculators
Find out what concrete will cost — by yard, square foot, or project type.
Concrete Slab Cost Calculator
Full installed cost estimate — volume, bags, labour, finish, and reinforcement.
Estimate cost →Concrete Cost Per Yard
See what ready-mix costs per cubic yard in your area, with delivery and waste.
Estimate cost →Concrete Driveway Cost
Estimate the total cost of a concrete driveway — from pour to finished surface.
Estimate cost →Concrete Patio Cost
Work out what a concrete patio will cost — size, thickness, and finish options.
Estimate cost →Concrete Calculators Explained
Quick guide to each calculator — what it does and when to use it.
Concrete Slab Calculator
Estimates the volume of concrete needed for flat, rectangular pours — driveways, patios, garage floors, and walkways. Enter length, width, and thickness to get your result in cubic yards. This is the most common starting point for any concrete project. Use it before calling a supplier to know exactly how much to order.
Calculate concrete volume →Concrete Bag Calculator
Tells you how many 40, 60, or 80 lb bags of premix you need for your project. An 80 lb bag covers roughly 0.45 cubic feet — useful for small pours, repairs, and fence post holes. For anything over 1–2 cubic yards, ready-mix is usually cheaper and faster. Use the bag calculator for precise counts before your next hardware store run.
Calculate bags →Concrete Block Calculator
Counts how many CMU (concrete masonry unit) blocks you need to build a wall to a given height and length. Standard US blocks measure 8×8×16 inches. Enter your wall dimensions and the calculator handles the count, including a standard 10% waste buffer. Ideal for retaining walls, foundations, and block fencing.
Calculate blocks →Concrete Cost Per Yard
Ready-mix concrete in the US typically runs $120–200 per cubic yard, plus a delivery fee of $100–200. Bagged concrete works out to $300–480 per yard equivalent — cost-effective only for small pours under one yard. Your final project cost also depends on labor, forming, and finishing. Use a cost calculator to build a complete estimate.
Estimate concrete cost →Concrete Cost Per Square Foot
Installed concrete costs $4–12 per square foot for most residential projects. Thickness matters — a 6-inch slab costs roughly 33% more than a 4-inch slab of the same footprint. Decorative finishes, colored concrete, and stamped patterns add significantly to this figure. Use a concrete slab cost calculator with your square footage and thickness for a reliable estimate.
Calculate slab cost →Concrete Driveway Cost
A concrete driveway typically costs $4–10 per square foot installed, or $3,000–7,500 for a standard two-car driveway. Cost depends on slab thickness, local labor rates, removal of existing material, and finish type. Stamped and colored concrete add $3–12 per square foot. Always get at least two quotes from local contractors before committing.
Estimate driveway cost →Concrete Patio Cost
A concrete patio costs $3,000–5,500 on average for a 300 sq ft slab, or roughly $6–12 per square foot installed. Stamped and decorative concrete can push that to $15–25 per square foot. A basic broom-finish patio is the most affordable option. Use a concrete slab cost calculator to estimate your patio before budgeting for the full project.
Estimate patio cost →How to calculate concrete in cubic yards
All concrete in the US is ordered and priced by the cubic yard. To find the volume you need, multiply the length and width of your slab (both in feet) by the thickness. Because thickness is usually given in inches, divide it by 12 first to convert to feet. That gives you cubic feet.
Formula
Cubic yards = (Length ft × Width ft × Thickness in ÷ 12) ÷ 27
It helps to think of it in two steps: first get cubic feet, then convert. A slab that is 10 ft × 10 ft × 4 inches thick contains 33.3 cubic feet. Divide by 27 and you get 1.23 cubic yards. That's a manageable amount to mix by hand — use the concrete bag calculator to get the exact bag count for your project.
Worked example: 20 × 12 ft driveway slab
Say you're pouring a driveway that is 20 feet long, 12 feet wide, and 4 inches thick — a common residential size. Here's the step-by-step:
Convert thickness to feet
4 in ÷ 12 = 0.333 ft
Calculate cubic feet
20 × 12 × 0.333 = 80 cu ft
Convert to cubic yards
80 ÷ 27 = 2.96 cu yd
Add 10% waste
2.96 × 1.10 = 3.26 cu yd to order
At 4 inches thick, this driveway needs just under 3 cubic yards. Bump it to 6 inches — the thickness recommended if you park trucks or an RV — and the same footprint jumps to 4.44 cubic yards. Getting the thickness right before ordering is the single most important step.
How many 80 lb bags of concrete do you need?
An 80 lb bag of premix concrete (such as Quikrete or Sakrete) covers approximately 0.45 cubic feet when mixed. Since there are 27 cubic feet in a cubic yard, you need about 60 bags per cubic yard. Here's a quick reference for common project sizes:
0.5 cu yd
30 bags
+10% waste: 33 bags
1 cu yd
60 bags
+10% waste: 66 bags
2 cu yd
120 bags
+10% waste: 132 bags
3 cu yd
180 bags
+10% waste: 198 bags
Mixing 60 bags by hand is a full day's work for one person. At around 2 cubic yards and above, most contractors switch to ready-mix, which arrives pre-blended and pours quickly. Bags are best for small pours, repairs, or projects where you need to work in stages. Need a precise bag count? Use the bag calculator →
What does concrete cost per cubic yard?
Concrete pricing varies by region, season, and supply method. These are rough national averages for 2025–2026:
Bagged concrete (80 lb)
$5–8 per bag
≈ $300–480 per cubic yard equivalent
Best for small pours under 1 yard. Convenient but expensive at scale.
Ready-mix (truck delivery)
$120–200 per yard
Plus delivery fee, typically $100–200
Most cost-effective for anything over 1–2 yards. Consistent quality, faster pour.
For a 3-yard driveway using ready-mix, expect to pay $360–600 for the concrete alone, plus delivery and any finishing or labor costs. Always get at least two quotes from local suppliers — regional prices can differ by 30% or more. For a full project estimate, use the concrete slab cost calculator.
Common mistakes when estimating concrete
Skipping the waste buffer
Ordering exactly what the formula says almost always leaves you short. Ground isn't perfectly level, forms shift, and mixing absorbs extra. Always add at least 10%.
Mixing up cubic feet and cubic yards
Many people calculate in cubic feet and forget to divide by 27. One cubic yard is 27 cubic feet — a mistake here means ordering 27× too much or too little.
Underestimating slab thickness
A 4-inch slab and a 6-inch slab of the same footprint require 50% more concrete. Confirm thickness requirements before calculating, especially under driveways.
Forgetting the sub-base
Concrete poured directly onto soft soil can crack and sink. A 4–6 inch compacted gravel base is standard. This doesn't change your concrete volume but affects overall excavation depth.
Where this calculator is used
This tool works for any rectangular concrete pour. Common uses include:
Driveways
Typically 4–6 in thick. Single-car: ~2–3 cu yd. Double: 4–6 cu yd.
Patios
Usually 3–4 in. A 16 × 20 ft patio at 4 in = ~4 cu yd.
Garage floors
Minimum 4 in — 6 in if supporting vehicles. 20 × 20 ft = ~5 cu yd.
Footings
Depth varies by frost line and load. Poured separately from the slab.
Fence posts
Small individual pours. Use the calculator per post for bag counts.
Shed slabs
3–4 in is typical. A 12 × 16 ft shed base needs roughly 1.8 cu yd.
Frequently asked questions
How do I calculate cubic yards of concrete?
Multiply length (ft) × width (ft) × thickness (ft — convert inches by dividing by 12). That gives cubic feet. Divide by 27 to get cubic yards. Then add 10% for waste.
How many 80 lb bags of concrete per cubic yard?
Approximately 60 bags. An 80 lb bag yields about 0.45 cubic feet. Since a cubic yard equals 27 cubic feet: 27 ÷ 0.45 = 60 bags. Buy 66 if adding 10% waste.
What is the difference between cubic feet and cubic yards?
One cubic yard equals exactly 27 cubic feet (3 ft × 3 ft × 3 ft). Ready-mix suppliers always quote in cubic yards. If your calculator gives cubic feet, divide by 27 before ordering.
How thick should a concrete slab be?
Residential driveways: 4 inches minimum, 6 inches if you park heavy vehicles. Patios and walkways: 3–4 inches. Garage floors: 4–6 inches. Footings vary by soil and load.
What does a yard of concrete cost?
Ready-mix typically runs $120–200 per cubic yard plus a delivery charge of $100–200. Bagged concrete (80 lb bags at $5–8 each) works out to $300–480 per equivalent cubic yard — cost-effective only for small jobs.
When should I use ready-mix instead of bags?
Once you're at 1.5 cubic yards or more, ready-mix is usually cheaper and far faster. Mixing 90 bags by hand takes several hours and risks an uneven mix. Ready-mix ensures consistent strength throughout the pour.
Disclaimer
This calculator provides estimates only and should be used for planning purposes. Actual concrete quantities depend on ground conditions, form accuracy, pour technique, and material yield — all of which vary in practice. Always confirm quantities with your supplier before ordering.
Cost figures are approximate national averages and may not reflect your local market. Bag yields are based on manufacturer averages — check the label for the specific product you buy.