# Concrete Calculator

> Concrete calculator: work out slab volume, cubic yardage, and how many concrete bags you need from your slab dimensions. Free, no signup, runs locally.

- **Canonical URL:** https://boringtoolskit.com/concrete-calculator/
- **Category:** Construction & Measurement
- **Evidence level:** authored-methodology
- **Reviewed:** August 2026
- **Last verified:** 2026-10-12
- **Privacy:** Inputs and results stay in this browser unless the page clearly labels an external request.

## How it works

volume = length × width × depth; convert cubic feet to cubic yards by dividing by 27

## Worked example

A 10 ft by 12 ft slab at 4 inches deep is about 1.48 cubic yards before waste.

## Assumptions

- Depth is converted to feet
- Subgrade and form dimensions are accurate
- Overage is considered for spills/uneven grade

## Common questions

### How much extra concrete should I order?

Small jobs often add 5–10%, but confirm with the supplier and contractor.

### Why cubic yards?

Ready-mix concrete is commonly ordered by cubic yard in the US.

## Related tools

- /paver-calculator/
- /gravel-calculator/
- /construction-estimate-tools/

## Sources

- [Calculation methodology and verification standard](/methodology/)

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*Local planning estimate. Verify current terms, rates, and policies before acting.*