Concrete Calculator
Calculate concrete volume in cubic yards and cubic meters, ready-mix truckloads, and pre-mixed bag quantities with customizable waste factor.
= 1.13 m³ (40 cu ft net)
Did this calculation save you time?
Student ProjectHi! I'm a student developer building Calculat in my spare time. I was tired of searching for basic math tools and having to click through 10 spammy popups, loan ads, and cookie trackers.
I keep this website 100% free, private, and ad-free. If this helped you with your homework, project, or finances today, bookmarking this page or telling a friend helps me keep building more free tools!
What Is a Concrete Calculator?
A concrete calculator computes the exact volume of ready-mix concrete required for slabs, foundations, footings, and driveways. It converts square footage and depth into cubic yards and cubic meters, incorporating a standard 10% safety overage for subgrade irregularities and spillage.
How to Use This Calculator
- Enter length and width of the pour area in feet.
- Enter the slab thickness in inches (4" for patios/sidewalks, 5–6" for driveways).
- Set your preferred waste contingency percentage (default is 10%).
- Read total cubic yards, cubic meters, and equivalent 80lb/60lb premix bags.
Cubic Yards Concrete Formula
\text{Cubic Yards} = \frac{\text{Length (ft)} \times \text{Width (ft)} \times \left(\frac{\text{Thickness (in)}}{12}\right)}{27} \times \left(1 + \frac{\text{Waste}\%}{100}\right)There are 27 cubic feet in one cubic yard. Dividing cubic feet by 27 and adding the waste percentage gives the volume to order from the concrete dispatch plant.
Worked Example
Scenario: Ordering concrete for a 20 ft by 20 ft residential driveway slab poured 5 inches thick with a 10% waste buffer.
Calculate cubic feet: 20 × 20 × (5 ÷ 12) = 400 × 0.4167 = 166.67 cu ft.
Convert to cubic yards: 166.67 ÷ 27 = 6.17 cu yds.
Add 10% contingency: 6.17 × 1.10 = 6.79 cu yds.
Order quantity: 7.0 cubic yards from the ready-mix batch plant.
Tips & Key Notes
- Always round up to the nearest 0.25 or 0.5 cubic yard when ordering from ready-mix suppliers; running short mid-pour creates cold joints.
- Standard 4-inch slabs are sufficient for patios and walkways, but vehicle driveways require a minimum of 5 inches with rebar reinforcement.
- Factor in subgrade variance; un-compacted gravel bases often consume an extra 5% to 8% in depth depression.
Frequently Asked Questions
How do I calculate how many yards of concrete I need?
Multiply Length (ft) × Width (ft) × Thickness (ft), then divide by 27. To convert thickness from inches to feet, divide by 12. For example, for a 10x10 slab at 4 inches: 10 × 10 × 0.333 ÷ 27 = 1.23 cubic yards. Add 10% for waste (1.35 yards).
How much does a cubic yard of concrete weigh?
Normal-weight ready-mix concrete weighs approximately 4,000 pounds (2 US tons) per cubic yard, or about 145 to 150 lbs per cubic foot.
What is the minimum truckload for ready-mix concrete delivery?
Most ready-mix concrete trucks hold 9 to 11 cubic yards. Ready-mix companies typically require a minimum order of 1 to 3 yards, often charging a "short load fee" for orders under 5 or 6 yards.
When is it cheaper to buy bags versus ordering a concrete truck?
As a rule of thumb, if your project requires under 1.5 to 2 cubic yards (~70 to 90 eighty-pound bags), buying bags is typically more cost-effective. For more than 2 cubic yards, ordering a delivery truck saves immense time and labor.
Related Calculators
Explore similar toolsConcrete Slab Calculator
Calculate ready-mix concrete yardage, gravel base tonnage, and rebar reinforcement grid sticks for slabs, patios, and garage floors.
Concrete Block Calculator
Calculate standard 8x8x16 CMU blocks, mortar bags, vertical rebar, and core fill grout for masonry foundation and retaining walls.
Quikrete Calculator
Calculate Quikrete concrete bags for slabs, fence posts, and footings including standard yellow bag and Fast-Setting red bag mixes.