Construction Calculators
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Concrete Calculator
Calculate concrete volume and material requirements for slabs, footings, columns, and stairs. Get accurate estimates instantly.
Concrete Volume Calculator
Calculate concrete requirements for slabs, footings, columns, and stairs
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How the Concrete Calculator Works
Ready-mix in Phoenix runs roughly $145 to $165 per yard in Q1 2026, and Northeast metros are pushing $190 to $220, so getting the cubic-yard count right is what separates a tight bid from a giveaway. This calculator handles the volume math for slabs, footings, piers, columns, and stair pours using a 3,000 to 4,000 psi mix as the default assumption.
On the order side, suppliers in most US markets enforce a 9 or 10 cubic-yard minimum and charge a short-load fee around $35 to $50 per yard under that threshold. Confirm mix design (per ASTM C94), aggregate size, slump, admixtures, and pump access before you send the bid; the volume number is just the start of a real concrete estimate.
Volume math
- Cubic feet = length (ft) x width (ft) x depth (ft)
- Cubic yards = cubic feet / 27
- Order quantity = cubic yards x (1 + waste factor)
- 80 lb bags = cubic yards / 0.022
Estimating Steps and Checks
Break the pour into shapes
Take off slabs, footings, columns, and stair stringers as separate shapes. Convert depth from inches to feet (divide by 12) before any multiplication or you will be off by an order of magnitude.
Run the volume
Length x width x depth in feet, divided by 27, gives cubic yards. For tapered footings or stepped pours, average the cross sections instead of using the deepest point.
Pad for waste and the supplier minimum
Add 5 percent for formed, well-prepped pours; bump to 10 percent if subgrade is uneven or hand-excavated. Then round up to whole yards or to the supplier minimum, whichever is larger.
Layer in everything else
Rebar or mesh, vapor barrier, expansion joints, pump or buggy time, finisher hours, sealer, and saw-cut control joints all live outside the volume number. Quote them line by line.
Common Checks
- A 4-inch slab consumes 0.01235 cubic yards per square foot before waste — useful as a sanity check on a takeoff.
- Watch out: cold-weather pours below 40 F typically need accelerator or hot water, which adds $8 to $15 per yard at most regional plants.
- In California and Oregon, plants frequently substitute Type IL portland-limestone cement (per ASTM C595) without notice — confirm if your spec is Type I/II only.
- Field tip: a pour crew of four averages 15 to 20 cubic yards per day on a slab-on-grade. If your quantity exceeds that, you are buying a second day of finishing.
Concrete Calculator FAQs
How do I calculate concrete yards?
Multiply length, width, and depth in feet, divide by 27, then pad for waste. The math is trivial; the trap is leaving depth in inches.
My supplier wants a minimum order — does that mean I pay for unused yards?
Yes. Most plants bill the minimum (commonly 9 or 10 yards) plus a short-load fee on anything below it. For a 6-yard pour you usually owe a $150 to $250 short-load surcharge unless a partial-load supplier services your area.
How many 80 lb bags equal a cubic yard?
Roughly 45 bags. At Home Depot or Lowes pricing of about $5.50 a bag, that is $250 in materials before tax — competitive with ready-mix only for very small or remote pours where delivery is impossible.
Bags or ready-mix for a 1-yard footing?
One yard sits in the gray zone. If you have a mixer and labor on site already, bags work. If finishing time matters or the pour is structural, ready-mix gives you a consistent slump and a delivery ticket for QC records.