Concrete Calculator
Works out volume from slab dimensions, adds a spillage allowance and converts to cubic yards and 80 lb bag equivalents.
- 80 lb bags
- 123
- Slab area
- 200 sq ft
- · Above roughly 1 cubic yard, ready-mix is usually cheaper and far easier than bags.
- · Order slightly over — a short pour cannot be fixed after the first load sets.
How to use the Concrete Calculator
-
01
Measure the slab length and width in feet.
-
02
Enter the designed slab thickness in inches.
-
03
Allow for spillage, an uneven base and formwork variation.
-
04
Use cubic yards for ready-mix quotes or the bag count for small hand-mixed work.
Frequently asked questions
What waste allowance should I use?
Ten percent is a sensible planning allowance for a straightforward slab on a prepared base.
When should I order ready-mix?
Ready-mix is usually more practical above roughly one cubic yard, especially where the pour must be continuous.
Does this specify the slab thickness?
No. Thickness, reinforcement and base preparation depend on loads and ground conditions and should be designed for the project.
Other tools
Paint Calculator
Work out gallons of paint and primer for any room, including doors and windows.
Flooring Calculator
Boxes of flooring needed for any room, with a waste allowance for cuts and pattern.
Tile Calculator
Tiles, grout and adhesive for floors or walls, with breakage allowance.
Wallpaper Calculator
Rolls of wallpaper needed, accounting for pattern repeat.
These calculators give planning estimates based on the figures you enter. They are not a substitute for a site survey, a structural or load calculation, or professional advice. Always confirm quantities with your supplier or contractor before ordering.