Concrete Calculator USA 2026
Calculate the exact volume of ready-mix concrete you need for slabs, footings, driveways and pads in cubic yards, cubic meters and 60/80 lb bags.
Concrete Calculator USA 2026 — the quick answer
Calculate the exact volume of ready-mix concrete you need for slabs, footings, driveways and pads in cubic yards, cubic meters and 60/80 lb bags.
| Formula | Volume (ft³) = Length × Width × Thickness ÷ 12 → Yards = ft³ ÷ 27 |
|---|---|
| Category | Concrete |
| Cost basis | 2026 USA averages (USD) |
Output
Planning estimate
Time to use
Under a minute
Last reviewed
2026
Built for
DIYers & trades
Enter your measurements
Results
Volume
133.3 ft³
3.78 m³
Cubic yards (with 10% waste)
5.43 yd³
60 lb bags needed
326
80 lb bags needed
245
Calculation steps
- 1.Volume = 20 × 20 × (4 ÷ 12) = 133.33 ft³
- 2.Cubic yards = 133.33 ÷ 27 = 4.94 yd³
- 3.With 10% waste = 4.94 × 1.10 = 5.43 yd³
- 4.80 lb bags = ⌈5.43 × 45⌉ = 245
Includes a standard waste allowance. Verify with your supplier before ordering.
What this calculator does
Estimates the volume of ready-mix concrete you need — in cubic yards, cubic meters and 60/80 lb bag counts — plus a 10% waste allowance so you don't run short mid-pour.
When to use it
- Planning a slab, patio, footing, driveway or sidewalk pour.
- Comparing bagged vs. ready-mix truck pricing.
- Sizing rebar, mesh and vapor barrier by area.
Common mistakes
- Forgetting to convert thickness from inches to feet before multiplying.
- Ordering exact volume with zero waste — always add 5–10%.
- Ignoring compaction: over-excavated subgrade sinks the finished slab.
Pro tips
- Order 10% extra for slabs, 15% for uneven ground or complex forms.
- For driveways, use 6" thickness and #4 rebar at 18" on-center.
- Pour early morning in summer to avoid flash-set from heat.
What the Concrete Calculator works out for your concrete job
Calculate the exact volume of ready-mix concrete you need for slabs, footings, driveways and pads in cubic yards, cubic meters and 60/80 lb bags.
Enter Length (ft), Width (ft) and Thickness (in) and the concrete calculator returns Volume, Cubic yards (with 10% waste), 60 lb bags needed and 80 lb bags needed instantly — no signup, no spreadsheet and no install. Every figure updates as you type so you can test two or three concrete scenarios before you commit to an order or a bid.
Concrete numbers this page gives you
The output is written for a real supply run: quantities and figures you can hand to a supplier or drop straight into a bid for concrete work.
- Volume — recalculated on every input change.
- Cubic yards (with 10% waste) — recalculated on every input change.
- 60 lb bags needed — recalculated on every input change.
- 80 lb bags needed — recalculated on every input change.
How to estimate concrete step by step
The math behind this page is Volume (ft³) = Length × Width × Thickness ÷ 12 → Yards = ft³ ÷ 27. Nothing is hidden — the formula, the assumptions and the waste allowance are all printed on the page so you can re-check the result by hand.
Worked example: A 20 ft × 20 ft × 4 in patio = 400 × 0.333 = 133.3 ft³ = 4.94 yd³. With 10% waste ≈ 5.43 yd³.
- Measure the concrete area or run and write down Length (ft), Width (ft) and Thickness (in).
- Enter the figures above and read the concrete result.
- Add the recommended waste allowance before you order.
- Save or download the estimate so your supplier and your crew work from the same numbers.
Concrete searches this page answers
Homeowners, DIYers and contractors reach this concrete page looking for the same handful of answers. Each of these is answered above with the formula shown:
- Concrete calculator
- How much concrete do I need
- Concrete estimator online
- Concrete quantity takeoff calculator
- Free concrete calculator app USA
- Concrete material calculator 2026
Before you order concrete: quick checklist
- Re-measure the concrete area once before ordering — a second check is cheaper than a second delivery.
- Keep the stated waste allowance in the order; cuts and breakage are normal on concrete work.
- Confirm coverage or unit size with your actual supplier — concrete pack sizes vary by brand.
More concrete planning tools
Pair this concrete estimate with the rest of BuildMate: a full calculator index, an AI planner that turns a plain-English description into a materials list, and step-by-step guides for the trade work itself.
Targeted searches: concrete calculator · how much concrete do I need · concrete estimator online · concrete quantity takeoff calculator · free concrete calculator app USA · concrete material calculator 2026
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Disclaimer: This is a planning estimate produced from the formula shown above. Actual quantities vary with site conditions, layout, offcuts and installer practice. Verify with your supplier or contractor before ordering, and see our methodology.
How it works
- 1Enter length and width of the pour in feet.
- 2Enter thickness in inches (4" is standard for a patio, 6" for a driveway).
- 3We convert to cubic yards, add a 10% waste allowance, and estimate 60 lb and 80 lb bag counts.
Formula
Worked example
A 20 ft × 20 ft × 4 in patio = 400 × 0.333 = 133.3 ft³ = 4.94 yd³. With 10% waste ≈ 5.43 yd³.
Frequently asked questions
How much waste should I add?
10% is standard for slabs; 15% for uneven ground or complex forms.
How many 80 lb bags per cubic yard?
About 45 bags of 80 lb pre-mix per cubic yard.
What thickness for a driveway?
6 inches for cars, 8 inches for heavy vehicles.
How do I use the Concrete Calculator?
Enter Length (ft), Width (ft) and Thickness (in). The concrete calculator instantly returns Volume, Cubic yards (with 10% waste), 60 lb bags needed and 80 lb bags needed, along with the formula and every calculation step so you can verify the result.
How much concrete do I need?
It depends on your measurements, so run the concrete numbers above rather than using a rule of thumb. The calculator applies the standard trade formula plus a stated waste allowance, which is what stops you from coming up short mid-job.
What does the Concrete Calculator include in its result?
It reports Volume, Cubic yards (with 10% waste), 60 lb bags needed and 80 lb bags needed. The underlying formula is Volume (ft³) = Length × Width × Thickness ÷ 12 → Yards = ft³ ÷ 27.
Is the Concrete Calculator free, and does it work on mobile?
Yes — it's free, needs no account, and runs in the browser on phone, tablet and desktop. Nothing is installed and your saved concrete estimates stay on your own device.
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