What Is a Cubic Yard?
A cubic yard equals 27 cubic feet. A standard concrete truck delivers 8 to 10 cubic yards per load, so knowing your total helps plan delivery.
Concrete estimating
Concrete Calculator – Estimate Volume, Weight & Bags
Free concrete calculator for slabs, walls, footings, columns, round slabs, tubes, curbs and stairs. Enter your measurements, choose your units, and this online concrete calculator estimates volume in cubic feet, cubic yards and cubic meters, plus concrete weight and 60 lb or 80 lb bag counts. Use it for driveways, patios, fence posts and staircases before ordering ready-mix or bagged concrete.
Estimate Concrete Volume, Weight, and Bags
Choose Shape
How to use
How to Use This Concrete Calculator
Choose the shape that matches your project — slab, column, tube, curb or stairs — then enter the dimensions and units. The concrete calculator converts everything into volume, weight and bag count.
- Pick the closest shape for the concrete structure.
- Enter the project dimensions from your forms or plans.
- Select the correct unit for each measurement.
- Set the quantity for multiple matching sections.
- Review volume, weight and bag count before ordering.
- Add a waste allowance before ordering ready-mix or bags.
Measurements
Cubic Feet, Cubic Yards & Cubic Meters
This concrete calculator shows results in cubic feet, cubic yards and cubic meters. In the US, ready-mix concrete is priced by the cubic yard. For small DIY projects, cubic feet and concrete bags are often more practical.
Convert Cubic Feet to Cubic Yards
Divide cubic feet by 27. For example, 54 cubic feet equals 2 cubic yards. Suppliers quote per cubic yard and may charge extra for small loads.
Cubic Meters for Metric Projects
One cubic meter equals 35.3 cubic feet. Many countries outside the US order concrete by the cubic meter.
Weight & bags
Concrete Weight & Bag Estimates
Normal-weight concrete weighs about 133 to 150 lbs/ft³, or roughly 2,130 kg/m³. The concrete calculator estimates weight in pounds and kilograms, and counts 60 lb or 80 lb bags rounded up to avoid running short.
- Calculate volume in cubic feet using the matching shape.
- The calculator multiplies volume by density to get weight.
- Divide weight by bag size for a raw bag count.
- Round up — partial bags are not sold.
- Add a waste allowance if you want bags to include extra material.
Shapes
Choose a Concrete Calculator by Shape
Pick the shape that matches how the concrete will be formed. For mixed projects, calculate each part separately and add the results.
Concrete Slab Calculator
For driveways, patios, garage floors, shed pads and sidewalks. Enter length, width, thickness and quantity. A small thickness change can noticeably increase volume.
Wall and Square Footing Calculator
Same rectangular formula for walls, footings and structural pads. Enter length, width, depth and quantity.
Column and Post Hole Calculator
For round footings, fence post holes, deck posts and pier foundations. Enter diameter, depth and quantity.
Round Slab Calculator
For circular pads, round patios, fire pit bases and circular shed bases. Enter outside diameter, thickness and quantity.
Tube and Hollow Cylinder Calculator
For hollow columns, sonotube forms, sleeves and pipe-like structures. Enter outer diameter, inner diameter, height and quantity.
Curb and Gutter Calculator
For sidewalk edges, road curbs, drainage channels and gutter sections. Enter curb depth, gutter width, curb height, flag thickness, length and quantity.
Concrete Stairs Calculator
For steps, porch steps and small stair projects. Enter tread depth, riser height, width, platform depth, step count and quantity.
Concrete Block Calculator
For concrete block and cinder block walls. Estimate block quantity, mortar bags and material cost with country-aware imperial or metric units.
Results
Concrete Calculator Results Explained
The result area converts the same estimate into volume, weight and bag counts so you can compare ready-mix and bagged options.
Volume in Cubic Feet, Yards and Meters
Ready-mix is usually ordered by cubic yard, smaller projects by cubic feet or bags, and metric projects by cubic meters.
Weight in Pounds and Kilograms
Weight helps with transport, delivery and site access planning, using a normal-weight concrete density assumption.
Bag Calculator for 60 lb and 80 lb Bags
For small slabs, post holes, steps and DIY repairs where a truck is not needed. Bag counts are rounded up after the waste allowance.
Reference
Concrete Calculation Formulas
Each formula runs after converting every dimension to feet, then converts the result into cubic yards and cubic meters. Different shapes need different geometry — a slab, cylinder, hollow cylinder, curb and stair do not share one formula.
Slab, Wall and Footing
Volume = length × width × thickness × quantity. Used for driveways, patios, pads, walls and square footings.
Cylinder and Round Slab
Volume = π × radius² × height × quantity. Used for post holes, round footings and circular pads.
Hollow Cylinder
Volume = π × (outer radius² − inner radius²) × height × quantity. Counts only the ring-shaped section.
Stairs
Volume = (width × run × rise × steps × (steps + 1) ÷ 2) + (width × platform × (steps + 1)) × quantity. Combines stepped section and landing.
Curb and Gutter
Volume = length × ((curb depth × curb height) + (gutter width × flag thickness)) × quantity. Combines raised curb and gutter flag.
Weight and Bags
Weight = volume × density. Bags = order weight ÷ bag size, rounded up. The bag count uses the waste-adjusted estimate.
Ordering guide
How Much Concrete Do I Need?
The amount of concrete depends on shape, dimensions, thickness and quantity. Measure the actual formed space when possible — excavated holes and handmade forms are rarely perfect. A waste allowance covers uneven ground, form movement, spillage and small errors.
Why Add a Waste Allowance?
Most contractors add 5% to 10% extra concrete. Complex shapes like stairs, curbs and tubes trend higher (~10%); simple flat slabs may be fine at 5%. The waste field in this concrete calculator is adjustable.
- For slabs and driveways, measure formed length and width plus planned thickness.
- For posts and footings, measure the actual hole or form diameter and depth.
- Add 5% to 10% for waste, form movement and spillage.
- Use ready-mix for larger pours; use bags for small repairs or isolated footings.
- For mixed projects, calculate each section separately and add the totals.
Ordering guide
Ready-Mix vs. Bagged Concrete
Choose based on project size, site access and timeline.
When to Order Ready-Mix
Order ready-mix for projects over 2 to 3 cubic yards, or when you need consistent quality across a large pour. Suppliers price per cubic yard with minimums of 1 to 3 yards.
When to Use Bagged Concrete
Bagged concrete works for post holes, small slabs, steps and repairs under 2 cubic yards. Comes in 60 lb and 80 lb bags; useful when a truck cannot reach the site.
FAQ
Frequently Asked Questions
How much concrete do I need?
It depends on the shape, dimensions, thickness and quantity. A concrete calculator converts your measurements into volume in cubic feet, cubic yards and cubic meters. Most projects should include a waste allowance.
How many bags of concrete do I need?
Depends on volume, bag size and product yield. This concrete calculator estimates 60 lb and 80 lb bags by converting volume into weight and rounding up.
How many cubic yards do I need?
Divide total cubic feet by 27. This concrete calculator shows cubic yards directly so you can order ready-mix by the cubic yard.
How do I calculate concrete for a slab?
Multiply length by width by thickness, then by quantity. The concrete slab calculator converts these into cubic feet, cubic yards and cubic meters.
How do I calculate concrete for a round slab or post hole?
Enter diameter and depth. The column calculator converts diameter to radius and uses the circular volume formula.
Should I order extra concrete?
Yes. Add 5% to 10% extra for waste, uneven ground, form variation and spillage. The concrete calculator applies your selected waste allowance.
What thickness should I use for a concrete slab?
Thickness depends on the project, load, subgrade, reinforcement and local code. This concrete calculator estimates volume for any thickness you enter.
Can this concrete calculator estimate weight?
Yes. It estimates weight in pounds and kilograms from the calculated volume using a normal-weight concrete density.