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.
Live calculator
Enter your details
Your estimate
Results
Partner pick
Masonry trowel setSlab math done — finish it like it was poured, not patched.Check current price ↗As an Amazon Associate, CalcForged earns 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.
Free printable
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.
Where should we send the PDF?
Gear for the job
Tools & materials people actually buy
Concrete mixer
For anything over a few bags, a mixer pays for itself in one pour.
Masonry trowel set
Finishing, edging, and grooving tools for a slab that looks poured, not patched.
Concrete forms
Reusable form boards and stakes keep the slab square while it cures.
Mixing tub
The no-mixer route: a heavy tub for hand-mixing bags on the spot.
As an Amazon Associate, CalcForged earns from qualifying purchases made through these links.