Tip: 5–10% is common to cover spillage and uneven subgrade.
Why use a concrete volume calculator?
A concrete volume calculator helps you estimate how much ready-mix concrete or how many bags you need before you order. Getting this number right can save money, avoid delays, and keep your project moving. If you order too little, you risk cold joints and extra delivery fees. If you order too much, you pay for material you cannot use.
This page is designed for common residential and light commercial shapes: slabs, walls, footings, and round columns. Enter your dimensions, apply a waste factor, and the calculator returns volume in cubic feet, cubic yards, and cubic meters.
Concrete volume formulas used
1) Rectangular slab
Volume = Length × Width × Thickness
- Length and width are entered in feet.
- Thickness is entered in inches and converted to feet.
- Great for patios, garage floors, and shed pads.
2) Concrete wall
Volume = Length × Height × Thickness
- Length and height in feet.
- Thickness in inches, then converted to feet.
- Useful for retaining walls and foundation walls.
3) Footing
Volume = Length × Width × Depth
- Length in feet.
- Width and depth in inches, then converted to feet.
- Ideal for strip footings under walls.
4) Round column (cylinder)
Volume = π × radius² × height
- Diameter in inches, converted to radius in feet.
- Height in feet.
- Useful for piers, sonotube forms, and posts.
How to estimate concrete accurately
- Measure each dimension at least twice.
- Break complex shapes into simple sections and calculate each one.
- Add 5% to 10% extra for waste and variation.
- Round your final order up, not down.
- Confirm minimum order quantities with your concrete supplier.
Bagged concrete vs ready-mix
The result includes estimated 60 lb and 80 lb bag counts. For larger pours, ready-mix is often faster and more consistent. Bagged concrete can work for small jobs like posts, small pads, or minor repairs. As a rule of thumb, once your project reaches around 1 cubic yard or more, compare ready-mix pricing and delivery.
Common mistakes to avoid
- Mixing units (feet and inches) without converting properly.
- Forgetting to include multiple sections or repeats.
- Ignoring slope, grade variation, or thickened edges.
- Skipping waste allowance.
- Ordering exactly the theoretical value with no buffer.
Quick FAQ
How many cubic feet are in 1 cubic yard?
1 cubic yard = 27 cubic feet.
How much extra concrete should I order?
Most projects use 5% to 10% extra. Difficult access, uneven ground, or complex forms may justify a larger buffer.
Can I use this as a slab calculator and footing calculator?
Yes. The tool includes slab, wall, footing, and column modes so you can estimate the most common concrete placements in one place.