How much concrete for a driveway that isn't a rectangle?
Shape the pour to your real measurements — drag or type the corners — and get the exact volume to order, in 3D.
Tap a side's length to type your tape measurement — the corner slides to match, exactly. In the same box you can curve that side out or in (round ends, radius corners, half-moon patios). Or drag corners (snaps to 6 in) or type coordinates below. Tap a dashed midpoint to add a corner; double-tap to remove.
Corners (ft′ in″)
→ across · ↓ down, from the top-left. Watch the side lengths on the diagram match your measurements.
- 1→↓
- 2→↓
- 3→↓
- 4→↓
📏 How to measure on site
Pace it off, run a tape, or use your phone's Measure app — whatever you have. Get each side's length, then match the corners here (drag or type).
Phone-measured? Those are field estimates (±a few percent). Great for planning the pour — confirm the critical numbers before a final order.
Result
Exact volume + 10% waste, rounded up to the ¼ yd³ trucks sell in — spillage and an uneven grade never read the plans.
Buying bagged mix instead?
≈ 134 bags (80 lb). For ready-mix from a truck, just order the 3.50 yd³ above.
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How is this calculated?
Using the tool
Pick a starting shape, then set the corners — drag them or type them — until the side lengths match your measurements. You get the exact volume to order, with your real shape in 3D.
The math
The area of your shape comes from the surveyor's (shoelace) formula over the corner coordinates — exact for any straight-sided shape. Volume = area × thickness (converted to feet); dividing by 27 gives cubic yards, the unit you order ready-mix in.
A curved side is a slice of a circle, found from two tape measurements: corner to corner (c) and how deep the curve is in the middle (s). Radius r = (c²/4 + s²) / 2s; the slice adds (curving out) or removes (curving in) r²(θ − sin θ)/2, with θ the angle the curve spans. Exact, not an approximation — and the perimeter follows the curve, for forms and edging.
Most US jobs pour ready-mix from a truck, so cubic yards is the number that matters — the bag count is there if you're doing a small bagged pour. The drop is shown in 3D for drainage planning but doesn't change the volume (under 1% for typical slopes). Add 5–10% waste for uneven subgrade.