Concrete is the one material where guessing the bin size gets expensive fast. Guess too small and you are waiting on a second haul with a half-demolished driveway. Guess a standard roll-off and you get an overage bill at pickup. Here is the math we use every day, and a calculator so you do not have to do it by hand.
Cubic yards in one minute
A cubic yard is a cube three feet on each side, 27 cubic feet. Dumpsters are sized in cubic yards. A 10-yard lowboy holds about 10 of them loaded level with the rail.
To find the cubic yards in a slab: length (ft) × width (ft) × thickness (inches) ÷ 12 ÷ 27. A 20-by-20 driveway at 4 inches thick is 20 × 20 × 4 ÷ 12 ÷ 27, about 4.9 cubic yards.
That is the solid number. It is not what goes in the bin.
Swell: why broken concrete takes more room than the slab did
Once you break a slab up, the pieces do not stack neatly. There is air between them. Broken concrete occupies roughly 30 to 50 percent more volume than the solid slab it came from. We use 1.4 as a working factor. So that 4.9-yard driveway becomes about 7 loose yards in the bin, which fits in one lowboy with a little room to spare.
Small pieces pack tighter than big slabs. If your crew breaks it into pieces smaller than a dinner plate, you will get closer to 1.3. If they are dropping whole panels in, plan on 1.5.
Slab calculator
Enter the slab you are removing. This uses the 1.4 swell factor and a 10-cubic-yard lowboy, and gives you the loose volume, the approximate weight, and how many bins to call for.
What heavy material weighs per cubic yard
Weight is the number that turns a cheap quote into an expensive one on the wrong bin. These are working figures for loose, broken material, which is what actually goes in a dumpster:
| Material (loose, broken) | Tons per cubic yard | Full 10-yard lowboy |
|---|---|---|
| Broken concrete | 1.2 – 1.5 | 12 – 15 tons |
| Broken asphalt | 1.1 – 1.3 | 11 – 13 tons |
| Dry dirt / fill | 1.1 – 1.3 | 11 – 13 tons |
| Wet clay soil | 1.3 – 1.5 | 13 – 15 tons |
| Brick and block | 1.2 – 1.5 | 12 – 15 tons |
| Sand or gravel | 1.3 – 1.5 | 13 – 15 tons |
| Roofing shingles | 0.9 – 1.2 | 9 – 12 tons |
Now compare that to a standard roll-off. A 25-yard includes 3 tons. A 40-yard includes 4. Two cubic yards of concrete, a small walkway, uses up the entire allowance of a 25-yard bin, and everything after that is billed at $60 to $115 per ton. That is the whole reason the lowboy exists, and why ours has no weight limit on clean loads of any material in this table.
Real Los Angeles examples
| Job | Solid yards | Loose yards | Weight | Bins |
|---|---|---|---|---|
| Two-car driveway, 20 × 20 ft, 4 in | 4.9 | ~7 | ~9.5 tons | 1 lowboy |
| Backyard patio, 15 × 12 ft, 4 in | 2.2 | ~3 | ~4 tons | 1 lowboy |
| Long driveway, 40 × 12 ft, 5 in | 7.4 | ~10.4 | ~14 tons | 1 lowboy, full |
| Pool deck, 600 sq ft, 4 in | 7.4 | ~10.4 | ~14 tons | 1 lowboy, full |
| Block wall, 60 ft × 6 ft, 8 in block | 8.9 | ~12.5 | ~17 tons | 2 lowboys |
| Garage slab, 20 × 22 ft, 6 in | 8.1 | ~11.4 | ~15 tons | 2 lowboys |
Notice how often the answer is exactly one lowboy. A 10-cubic-yard bin at 1.4 swell covers about 7 solid yards, which is a 4-inch slab of roughly 550 square feet. Most residential driveways, patios, and pool decks in LA fall under that. When a job runs over, a second lowboy is almost always cheaper than a bigger bin with overage.
Keep the load clean
No weight limit applies to clean, single-material loads. Concrete with rebar and mesh still attached is fine, recyclers expect it. What breaks the rule is mixing in non-concrete material: wood forms, drywall, trash, green waste. Once that happens the bin is a general refuse load with a 2-ton allowance, and the whole point of the lowboy is lost.
If your job has both, which most demos do, we set a lowboy for the concrete and dirt and a 25-yard for everything else, or we tell you the order to load a single bin. Our lowboy vs. roll-off guide covers the sequencing, and the concrete disposal guide covers where it all goes once it leaves your street.
Loading tips that matter for concrete
- Break it small. Dinner-plate pieces pack at 1.3 swell. Whole panels pack at 1.5. That is the difference between one bin and two on a big driveway.
- Load level, not mounded. Anything above the rail cannot legally leave your street. Level with the top is a full bin.
- Load from the truck side out. The bin has to lift evenly. Fill the end nearest the rails first, then work back.
- Dirt goes in dry. Wet clay is 30 percent heavier than dry fill. If you can wait a day after rain, do.
- Driveway, not street. A lowboy on your apron needs no permit in the City of LA. On the street it does. Our permit guide covers the exceptions.
Frequently asked questions
- How many cubic yards of concrete fit in a 10-yard lowboy?
- About 10 cubic yards of broken concrete, loaded to the rail. Because broken concrete swells 30 to 50 percent compared to the solid slab it came from, that is roughly 7 cubic yards of original slab, or a 4-inch-thick pad of about 550 square feet.
- How much does a lowboy full of concrete weigh?
- Broken concrete runs about 1.2 to 1.5 tons per loose cubic yard, so a full 10-yard lowboy of clean concrete weighs 12 to 15 tons. That is why standard roll-offs with 3 or 4 ton allowances are the wrong bin for it, and why our lowboy has no weight limit on clean loads.
- How do I calculate how much concrete I have?
- Length in feet times width in feet times thickness in inches, divided by 12, divided by 27. That is solid cubic yards. Multiply by 1.4 to get the loose volume once it is broken up. A 20 by 20 foot driveway at 4 inches is 4.9 solid yards, about 7 loose yards, one lowboy.
- Is there a weight limit on concrete in your lowboy?
- No. Clean, single-material loads of concrete, dirt, brick, asphalt, sand, gravel, or rock have no weight limit in our 10-yard lowboy. Fill it to the rail and we haul it. The only rule is keep it clean: once you mix in wood, drywall, or trash it becomes a general refuse load with a 2-ton allowance.
- Can I put rebar or wire mesh in with the concrete?
- Yes. Rebar and mesh attached to broken concrete are normal and accepted at concrete recyclers. What you cannot mix in is non-concrete material like wood forms, drywall, or trash, because that turns a clean recyclable load into mixed debris.