Home › Tools › Home & Construction
Free Concrete Calculator
Estimate cubic yards or cubic metres of concrete for a slab, plus bags and cost.
What is the Concrete Calculator?
Estimate cubic yards or cubic metres of concrete for a slab, plus bags and cost.
Volume is length times width times thickness, multiplied by the number of slabs, then increased by your waste allowance. The calculator converts it to cubic yards and cubic metres, and divides by about 0.6 cu ft per 80 lb bag or 0.45 cu ft per 60 lb bag.
Home and building jobs are easier to price when you know how much material you really need. A quick estimate also helps you avoid buying too little or too much.
How to use the Concrete Calculator
Using the concrete calculator takes a minute or two. Your entries are saved in this browser, so you can come back later and carry on.
Step 1
Enter the measurements of the area you are working on.
Step 2
Read the amount of material needed, including a waste allowance where relevant.
Step 3
Round up when you buy, and check the figures with your supplier.
Tips for better results
Add 5 to 10 percent for uneven ground, spillage and over-excavation, and measure the thickness at its deepest point. For structural pours such as footings or driveways, confirm thickness, reinforcement and mix with local building codes or a professional.
Add 5 to 10 percent for waste, cuts and mistakes.
Measure twice, order once, and check quantities with your supplier.
Privacy and where your data goes
Everything you type into the concrete calculator stays on your own device. Zapxa does not receive your numbers or documents. If you clear your browser data, your saved entries will be removed, so download a PDF of anything you want to keep.
Frequently asked questions
How many bags of concrete make a cubic yard?
A cubic yard is 27 cubic feet, so at about 0.6 cu ft per 80 lb bag it takes roughly 45 bags before waste. Check the yield printed on your bag brand.
Should I order extra concrete?
Yes, the waste field adds a margin, 10 percent by default. Running short mid-pour can cause cold joints, while a small surplus is easy to use for pads or discard.
Is the concrete calculator free?
Yes. It is free to use with no signup, no watermark and no usage limits.
Is my data private?
Yes. Your inputs are processed in your browser and saved only in its local storage. They are not uploaded to our servers.
Does it work on mobile?
Yes. Zapxa works on phones, tablets and desktops. Use the print button or download a PDF to keep a copy.
Related Home & Construction tools
- Paint Calculator — Estimate gallons or litres of paint for a room's walls, ceiling and number of coats.
- Tile Calculator — Work out how many tiles and boxes you need for a floor or wall area.
- Flooring Calculator — Calculate how many boxes of flooring a room needs, with waste and cost.
- Roofing Calculator — Estimate roof area, roofing squares and shingle bundles from the house footprint and pitch.
- Gravel Calculator — Estimate cubic yards and tons of gravel for a given area and depth.
- Mulch Calculator — Calculate cubic yards and bags of mulch needed for a garden bed.