Construction
Concrete calculator
Concrete is sold by volume, so the most useful estimate converts your dimensions into cubic feet and cubic yards before you order. Choose a rectangular slab or footing, or a round column, then enter your dimensions and waste allowance. The calculator uses standard geometry, converts 27 cubic feet to one cubic yard, and shows an 80-pound bag equivalent using an approximate 0.6 cubic-foot yield. Always compare the result with the yield printed on your specific mix.
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Concrete Calculator
Estimate concrete volume in cubic yards, plus waste and bag equivalents.
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Masonry trowel setSlab math done — finish it like it was poured, not patched.Paid link · Check current price ↗As an Amazon Associate I earn from qualifying purchases.The math, plainly
How it works
- 01
A slab or footing uses length × width × thickness, with thickness converted from inches to feet.
- 02
A round column uses π × radius² × height.
- 03
Cubic feet are divided by 27 to convert to cubic yards, then a 5–10% waste allowance is added for ordering. One 80-pound bag is treated as about 0.6 cubic feet.
Try a real scenario
12 × 10 slab
Inputs4-inch thickness and 10% waste
Result40.00 cu ft base volume, about 1.63 cu yd to order, or 74 bags.
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The home improvement math cheat sheet
Yards, bags, and waste — plus the paint, flooring, and mulch formulas — on two printable pages. One email, yours to keep. No spam.
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More options for this calculator
Concrete mixer (paid link)
For anything over a few bags, a mixer pays for itself in one pour.
Concrete forms (paid link)
Reusable form boards and stakes keep the slab square while it cures.
Mixing tub (paid link)
The no-mixer route: a heavy tub for hand-mixing bags on the spot.
As an Amazon Associate I earn from qualifying purchases.