How much concrete do you need? Slabs, footing runs and sonotube columns — type dimensions the way you read a tape (12' 6 1/2" parses, so does 3,5 m), and get cubic yards, bag counts, a rebar grid and the cost, live as you type. Free, no sign-up, no tracking.
Estimates use manufacturer-published bag yields and plain geometry (constants in the footer). Confirm quantities with your supplier — batching, minimums and short-load fees are theirs, not ours. The rebar figure is a simple grid: no laps, chairs or edge-cover offsets.
Slab: Concrete Estimator for iPhone does the same job this page does — free for one pour here — and then turns it into a jobsite quote:
Free to download, with a one-time $4.99 Pro unlock. No subscription, no ads.
length × width × thickness; a round column is π × (diameter ÷ 2)² × height × count. The math runs metric under the hood; feet and inches convert exactly (1 ft = 0.3048 m).12' 6 1/2", 6", 1/2", 12' 6, bare decimals, and explicit metric (3.5 m, 350 cm, 1200 mm — comma decimals fine). Garbage is refused with a message, never silently guessed.floor(span ÷ spacing) + 1, full-length runs. Laps, chairs and edge cover are on purpose not included here — that schedule is the app's job.The constants are the industry-published ones, restated in the footer. This page is not a digit-for-digit port of the app's quote engine — it's the same job the app does, free for one pour.
At 4 inches thick, 10 × 10 ft is 33.3 ft³ ≈ 1.24 yd³; with 10% waste, about 1.36 yd³ — or 62 bags of 80-lb mix. That's the calculator's opening example; change any number and it re-solves.
A cubic yard is 27 ft³. At published yields that's about 45 × 80-lb, 60 × 60-lb, 72 × 50-lb, or 90 × 40-lb bags.
Pick the column shape and enter the tube diameter, fill height and count. A 12-inch tube 4 ft deep holds about 3.14 ft³ — roughly 6 bags of 80-lb mix with 10% waste. Common tube sizes are 8", 10" and 12".
Ready-mix is quoted per cubic yard, delivered. Enter your supplier's per-yard price and the calculator multiplies it by your waste-included yardage. Suppliers batch in ¼-yd steps and often add a short-load fee on small orders — the delivered quote is theirs to give.
Around 1 yd³ (≈ 45 × 80-lb bags), hand-mixing a single continuous pour stops being practical. A transit mixer carries ~10 yd³. The calculator always shows both numbers so the comparison is in front of you.
For a formed slab on even, compacted subgrade — yes, it's the standard allowance. Go 15%+ for rough subgrade, irregular forms, or pump lines. Being short mid-pour means a cold joint; round up.