DailyUseCalc

Concrete Calculator

Calculate how much concrete you need for slabs, circular pads, columns, piers, and post holes, including bags, weight, allowance, and optional cost.

Measurements

Typical yield: 0.60 ft³ (17.0 L) per bag · Check your product bag for exact yield.

Ready-mix price (optional)
Bag pricing (optional)

Simple material planning

How to use the concrete calculator

Choose the concrete shape and measurement system, enter only the dimensions shown for that mode, select a quantity and allowance, then calculate. Optional pricing lets you compare ready-mix and bagged concrete without combining their costs.

  1. 1

    Choose a shape

    Slab, circle, column, or hole

  2. 2

    Enter dimensions

    Use the finished concrete size

  3. 3

    Set quantity

    Calculate repeated items

  4. 4

    Add allowance

    Account for project variation

  5. 5

    Compare supply

    Ready-mix and bag estimates

Concrete volume basics

How much concrete do I need?

Concrete volume starts with the finished shape. A rectangular slab uses length × width × thickness. A circular pad uses the area of a circle multiplied by thickness. Columns, piers, and post holes use cylindrical volume.

The calculator multiplies one-item volume by quantity before applying the selected allowance. It keeps measured volume separate from adjusted volume and rounds the ready-mix recommendation upward to the nearest 0.1 cubic yard.

Estimated weight uses a typical normal-weight concrete density of 145 lb/ft³. Actual concrete density and bag yield vary, so confirm product and supplier specifications before ordering.

Shape and supply guide

Slabs, pads, columns, and post holes

Slab concrete calculation

Measure the complete rectangular footprint and planned thickness. Quantity can represent repeated slabs with identical dimensions.

Circular pad calculation

Measure the full diameter across the widest point. The calculator determines circular area before applying thickness and quantity.

Concrete for columns and piers

Use the finished concrete diameter and height. Area is omitted from the primary result because volume is the meaningful purchasing measurement.

Concrete for post holes

V1 treats the entire cylindrical hole as concrete and does not subtract post displacement.

Concrete bags vs ready-mix

Bag estimates use typical published yields; ready-mix uses the rounded recommended order. Enter either or both prices to keep their cost estimates independent.

Allowance and cost

Plan extra concrete and compare costs

Extra allowance

Allowance is added after measured volume. No hidden waste factor is applied.

How many bags?

Adjusted cubic feet are divided by bag yield and rounded up to a whole bag.

Concrete cost estimate

Ready-mix cost can include delivery. Bag cost uses bag count × price per bag.

Answers before you order

Frequently asked questions

How much concrete do I need?

Choose the project shape, enter its measurements and quantity, then add an allowance. The calculator converts the adjusted volume into cubic yards, cubic feet, cubic meters, liters, bags, and estimated weight.

How many bags of concrete do I need?

Bag count uses the allowance-adjusted volume and the typical yield for the selected bag size. Always confirm the actual yield printed on your product bag.

Should I add extra concrete?

A modest allowance can cover uneven forms, subgrade variation, spillage, and measurement differences. Ten percent is a common planning example, but the appropriate amount depends on the project.

Can I calculate circular pads, columns, and post holes?

Yes. V1 supports slabs, circular pads, columns or piers, and full cylindrical post holes. Post displacement is not subtracted.

Does this calculator provide structural advice?

No. It estimates material volume, weight, bags, and optional costs. A qualified professional should determine thickness, strength, reinforcement, and structural requirements.

Can I use metric measurements?

Yes. Switching to Metric converts the current dimensions, while the results retain common purchasing conversions for easy supplier comparison.

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