Concrete Volume Calculator
We estimate concrete for common shapes—slabs, footings, columns, and tubes—then add your waste factor and convert to cubic yards/meters with 40/60/80-lb bag counts.
Your project
How to measure each shape
Concrete totals
How we computed your volume
Results interpretation: who our concrete estimator helps
- DIY patios & shed slabs: quick yardage and bag counts to avoid short loads.
- Footings & trenches: estimate pours for fences, decks, and retaining walls.
- Columns & sonotubes: choose tube diameter/height and count bags per pier.
- Pros: fast takeoffs during bids with a clear waste allowance.
Use cases & examples
Example 1 — Patio slab: 20 ft × 12 ft × 4 in, waste 10%, qty 1 → per unit ≈ 3.259 yd³; total bags (80-lb) ≈ 147.
Example 2 — Fence footings: trench 60 ft long × 12 in wide × 12 in deep, waste 10% → ft³ = 60×(12/12)×(12/12)=60 ft³; with waste 66 ft³ → 60-lb bags ≈ 147.
Example 3 — Porch piers: tubes 12 in diameter × 8 ft tall, qty 4, waste 8% → one tube ≈ 6.79 ft³; total ≈ 27.14 ft³ → 40-lb bags ≈ 91.
How to use our Concrete Volume Calculator
- Choose a shape (slab, footing, column, tube).
- Enter dimensions in feet/inches and the quantity.
- Add a waste percentage (5–15% is common).
- Select a bag size (40/60/80-lb) or use yardage for ready-mix.
- Review per-unit and total volumes and bag counts; copy the link to share.
Concrete volume — FAQ
How many 80-lb bags are in a yard of concrete?
About 45–50 bags depending on the published yield. Using 0.60 ft³ per 80-lb bag, 1 yd³ (27 ft³) requires 27 ÷ 0.60 ≈ 45 bags.
What waste percentage should we use?
We usually see 5–10% for formed slabs and tubes. Trenches or rough sub-grades can justify 10–15%. It’s safer to slightly over-order than to run short mid-pour.
Should we choose bagged mix or ready-mix?
Bagged is convenient below ~1 yd³ if labor is available. Above that, ready-mix often saves time and improves consistency. Check delivery minimums and access.
Do our estimates include rebar or gravel?
We estimate concrete volume only. Add reinforcement and base separately per your plans, code, or engineer.
Can we combine multiple shapes?
Yes—break complex pours into slabs, trenches, columns, and tubes, compute each volume, add waste, and sum totals.
Why do online calculators differ slightly?
Rounding methods, bag-yield assumptions, and waste factors differ. We show our assumptions next to the results.
Concrete Volume Planning: from Yardage to Bag Counts
We designed our Concrete Volume Calculator to remove guesswork on pour day. Accurate yardage prevents short loads, delays, and cold joints, while a sensible waste allowance covers real-world variability like trench over-dig and uneven sub-grade. Below we explain practical methods that crews and DIYers can use to plan confidently.
Choosing the right shape
Most projects reduce to four primitives: slabs (flat rectangles), footings (trenches), columns (rectangular posts), and tubes (cylindrical sonotubes). Break complex plans into these shapes and sum volumes. Irregular polygons? Split them into rectangles and triangles; for curved edges, approximate with short rectangles.
Setting thickness and depth
Typical slabs run 4–6 inches for patios and walkways. Footings are sized by frost depth and load; always follow your local code and engineer’s details. For tubes, verify the pier depth/diameter and add headroom for slope and bell if specified.
Waste factor: why it matters
Even with tight forms, concrete losses happen. We see 5–10% as a common starting point; add more for rough trenches, thick aggregate bases, or hand-mixing. Over-ordering by a small margin is cheaper than pausing a pour to source another partial load.
Bags vs ready-mix
For small jobs (a few tenths of a yard), bagged mix is convenient. As volumes approach 1 yd³, ready-mix typically saves labor and yields more consistent strength. Our bag counts use widely published yields: 40-lb ≈ 0.30 ft³, 60-lb ≈ 0.45 ft³, and 80-lb ≈ 0.60 ft³.
Preventing common mistakes
- Measuring slab thickness in inches but forgetting to convert to feet.
- Ignoring slope or thickened edges—segment and add those volumes.
- Underestimating trench depth variation; add a conservative waste factor.
- Assuming bag yields equal labeled weight; always use volume yields.
A fast field workflow
- Sketch the shapes and write dimensions next to each edge.
- Compute each shape’s volume; add waste; multiply by quantity.
- Sum totals and convert to yards and meters for suppliers.
- Decide bagged vs ready-mix; check truck access and schedule.
- Stage tools and curing materials before the pour.
Update the inputs above and we’ll keep the math straight—live—so you can focus on a clean, continuous pour.