A free concrete calculator for slabs, paths and footings, in cubic yards and bags of every size.
Work out the concrete for a slab, path or footing in cubic yards, and the bags of each size by QUIKRETE's yields.
Your numbers
Add an area for each slab, path or footing. The bags are QUIKRETE Concrete Mix, by its data sheet's yields.
Your result
Fill in the fields above to see your result.
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Paste the code into any page: WordPress, Webflow, Squarespace, Ghost or plain HTML. It's free with the credit under it, which links back to navid.me.
This free concrete calculator works out how much concrete a slab, a path or a footing needs, in cubic yards and cubic meters.
It also counts the bags of each size, from 40 to 90 pounds, by the yields on QUIKRETE's own data sheet.
I built it because concrete is worked out by volume but sold in bags, and turning one into the other is where projects come up short.
Here's the formula, a worked example, and the bag yields.
TL;DRKey takeaways
What is a concrete calculator?
A concrete calculator turns the size of a slab, a path, a post hole or a footing into the concrete it takes.
For a round post hole, pick the circle and type the distance across.
How concrete is measured
Area × thickness gives cubic feet. A cubic yard is 27 cubic feet, by the units in NIST Handbook 44.
The bags come from the QUIKRETE Concrete Mix No. 1101 data sheet.
| Bag | Yield |
|---|---|
| 40 lb | 0.30 ft³ |
| 50 lb | 0.375 ft³ |
| 60 lb | 0.45 ft³ |
| 80 lb | 0.60 ft³ |
| 90 lb | 0.675 ft³ |
A worked example
Here's the example the calculator loads: a 10 by 10 foot slab, 4 inches thick, with 10% extra.
100 × 4 ÷ 12 = 33.3 cubic feet. With 10% extra, that's 36.7 cubic feet, or 1.36 cubic yards. 36.7 ÷ 0.60 = 62 bags of 80 lb.
Mistakes to avoid
These are the slips that come up most.
- Forgetting to turn the thickness from inches into feet
- Ordering the exact volume with nothing extra
- Using these yields for another mix without checking its bag
Who is the concrete calculator for?
It's for anyone pouring a slab, a path or post footings, and these tools help around it.
- Cubic yard calculator – for any volume
- Gravel calculator – for the base under a slab
- Square footage calculator – for the area first
Count the bags before the pour, and you won't run out halfway.
Plan your money with your AI
Take your numbers further in
Concrete Calculator FAQs
Questions about the concrete calculator? Here's what to know.
A concrete calculator works out the concrete a slab, path or footing needs, in cubic yards and in bags.
Multiply length × width × thickness in feet for cubic feet, then divide by 27 for cubic yards.
At 4 inches thick with 10% extra, 62 bags of 80 lb, or 82 of 60 lb, by QUIKRETE's yields.
About 0.60 cubic feet, by QUIKRETE's data sheet for Concrete Mix.
27 ÷ 0.60 = 45 bags.
27 cubic feet: 3 feet by 3 feet by 3 feet.
Yes, switch to meters and type the thickness in centimeters.
Yes, it's free with no sign-up.
It runs in your browser, and your numbers stay on your device.
I did.
I'm Navid Moazzez, and I made the concrete calculator as one of my free tools on navid.me.
More about me.
Navid Moazzez
AI business strategist & AI OS builder
Navid Moazzez helps creators and founders master AI and build their own AI Operating System (AI OS) to automate their business and life.
Navid.me is reader-supported. When you buy through links on this site, I may earn an affiliate commission. Learn more.
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