A concrete calculator estimates the exact volume of concrete you need for any construction project — whether you are pouring a driveway slab, setting fence post footings, casting columns, or building steps. It converts your measurements into cubic yards or cubic meters, counts the bags required, and flags when a ready-mix truck delivery makes more financial sense than buying bags.
Concrete Estimator
Project Type
Slab Dimensions
Options
Project Breakdown
Your project needs 0 cubic yards. At this volume, ordering ready-mix concrete is typically more economical than buying individual bags. Contact local suppliers for pricing.
How to Use the Concrete Calculator
Ordering too little concrete means a costly second pour and a potential cold joint — a structural weak point where fresh concrete meets hardened concrete. Ordering too much wastes money and creates disposal problems. This concrete calculator helps you hit the right amount for any project, whether you are pouring a backyard slab, setting fence posts, casting deck columns, or building concrete stairs.
Step 1: Choose Your Project Type
Select one of the four project types at the top of the calculator. Each type shows the relevant dimension inputs for that pour geometry. Slab / Pad is for flat horizontal pours like patios, driveways, and garage floors. Footing / Wall covers continuous footings and foundation walls. Column / Post handles round cylindrical pours including post holes and deck piers. Stairs / Steps calculates the staircase volume as a triangular prism times the width.
Step 2: Enter Your Dimensions
Use the unit toggle to switch between imperial (feet and inches) and metric (meters and centimeters). For slabs and footings, enter length, width, and thickness or depth. Thickness for slabs is entered in inches because slabs are typically 3–6 inches thick. For columns, enter the diameter in inches and the height in feet, plus the number of columns. For stairs, enter the number of steps, the rise (vertical height of each step), the run (horizontal tread depth), and the total stair width.
Step 3: Set Your Waste Percentage
Concrete volume calculations assume perfectly formed, level surfaces. In practice, a portion is always lost to spillage, slightly deeper subgrade in spots, and residual concrete left in the chute or mixer drum. The default 10% waste factor is appropriate for most pours. Reduce it to 5% for very precise formwork; increase it to 15% for rough terrain or large pours where more waste is expected.
Step 4: Read Your Material Estimates
The calculator shows the total volume in cubic yards (or cubic meters in metric mode), the number of 60-pound bags, and the number of 80-pound bags. A standard 60-pound bag yields 0.017 cubic yards of mixed concrete; an 80-pound bag yields 0.022 cubic yards. Use these bag counts to shop at your local home improvement store. When your total volume exceeds about 1 cubic yard, the calculator shows a ready-mix advisory — at that scale, ordering a ready-mix truck is almost always cheaper and less labor-intensive than mixing bags.
Step 5: Add a Price for a Cost Estimate
Optionally enter the price per cubic yard or cubic meter from your local supplier. The calculator multiplies the total volume by the price to give you a quick material cost estimate. Ready-mix concrete typically costs $125–$200 per cubic yard in the United States, depending on region and mix specifications. This estimate covers materials only — add labor, form rental, and rebar costs separately for a full project budget.
FAQ
Is this concrete calculator free to use?
Yes, this concrete calculator is completely free with no signup required, no paywalls, and no limits. All calculations run entirely in your browser — your project dimensions are never sent to any server and stay private on your device.
Is my data private when I use this tool?
Absolutely. Every calculation runs locally in your browser using client-side JavaScript. No project dimensions, measurements, or personal information are ever transmitted to a server. Your data stays entirely on your device.
How many 60-pound bags of concrete do I need for a slab?
Each 60-pound bag of concrete yields approximately 0.017 cubic yards. To find the number of bags, divide the total cubic yards (including waste) by 0.017. For example, a 10×10 ft slab at 4 inches thick needs about 1.23 cubic yards, which requires roughly 73 bags of 60-pound concrete.
What is a standard concrete slab thickness?
For residential driveways and garage floors, 4 inches (10 cm) is the standard minimum thickness. Sidewalks and patios are typically 3–4 inches. Heavily loaded slabs — like those supporting vehicles over 3 tons — should be 5–6 inches thick. Footings and foundations are typically 8–12 inches deep.
Why should I add a waste percentage to my concrete order?
A waste factor of 5–10% accounts for spillage during pouring, slight variations in form dimensions, uneven subgrade that increases depth in spots, and residual concrete left in the mixer. Ordering slightly more than your calculated volume ensures you do not run short mid-pour, which can weaken the slab by creating a cold joint.
When should I use ready-mix concrete instead of bags?
Ready-mix concrete delivered by truck is more economical than bags for projects over about 1 cubic yard. Each standard ready-mix truck holds 9–10 cubic yards and has a minimum order (usually 1 cubic yard). For smaller projects, bagged concrete is more practical and avoids minimum order fees and short-load charges.
How do I calculate concrete for a round column or post hole?
The volume of a cylinder is π × radius² × height. The calculator does this automatically — enter the column diameter and height, along with the number of columns, and it computes the total volume. This works equally well for round post holes, pier footings, and deck supports.
Can I calculate concrete in metric units?
Yes. Use the unit toggle to switch between imperial (feet/inches) and metric (meters/centimeters). Results are shown in cubic meters when in metric mode. The bag calculations remain in imperial (60 lb and 80 lb bags) as they are the standard sizes sold globally, but the cubic meter volume is shown alongside.