Offline
No internet, no account required.
ACI 318
Validated against the standard.
PDF export
Pro-only. Generate professional reports.
$2.99 Pro
Lifetime unlock. No subscriptions.
How it works
Enter your values
Type in your inputs — the app fills code tables and constants for you, so there's nothing to look up.
Get a code-checked result
Instant answer with a clear PASS / FAIL and the exact ACI 318 reference behind every number.
Save & export
Keep a history of calculations and export a clean PDF report to share or attach to a permit (Pro).
What this calculator does
This app converts a slab, footing, column, or pier into cubic yards of concrete and the number of bags, so you order ready-mix or buy bags without coming up short on pour day.
The formula
Cubic yards = length (ft) × width (ft) × thickness (ft) ÷ 27
An 80-lb bag yields about 0.60 ft³ and a 60-lb bag about 0.45 ft³, so bag count = total ft³ ÷ bag yield.
Worked example
A 10 x 10 ft slab, 4 in (0.333 ft) thick: 10 × 10 × 0.333 ÷ 27 = 1.23 yd³. As 80-lb bags: 33.3 ft³ ÷ 0.6 = 56 bags — which is why anything this size goes ready-mix.
Related calculators
Set fence and deck footings alongside the fence calculator and deck calculator.
Concrete FAQ
How do I get cubic yards?
Multiply length by width by thickness, all in feet, then divide by 27 (the number of cubic feet in a cubic yard).
How many bags is that?
Divide the total cubic feet by the bag yield — about 0.60 ft³ for an 80-lb bag or 0.45 ft³ for a 60-lb bag. The app adds a small waste allowance.
Slabs, footings, and columns?
Yes. It handles rectangular slabs and footings as well as round columns and piers using their volume.
Does it work offline?
Yes, it runs 100% offline with no account. Free with rewarded ads; a one-time $2.99 Pro unlock adds PDF export and saved history.
Get Concrete Calculator on your phone
Free with rewarded ads · $2.99 lifetime Pro · iOS & Android. Works 100% offline on the job site.