A 10×10 patio slab doesn’t sound like much until you try to haul out the demolished pieces and discover you’re moving three and a half tons. A concrete weight calculator boils down to one number worth memorizing: standard cured concrete weighs about 150 pounds per cubic foot, which works out to 4,050 pounds — right at two tons — per cubic yard. Everything else is multiplication. This guide walks the math for slabs, bags, and yards, then covers where the numbers bite: pickup payloads, dumpster limits, and floor loading.
The Base Numbers
Memorize three figures and you can estimate anything:
- 150 lb per cubic foot — normal-weight cured concrete (the range is 145-155 depending on aggregate; 150 is the engineering standard)
- 4,050 lb per cubic yard — 27 cubic feet x 150 lb
- 12.5 lb per square foot per inch of thickness — the shortcut for slabs (150 ÷ 12)
Wet concrete weighs essentially the same as cured. Curing is a chemical reaction, not drying — only a few pounds of water per cubic yard ever evaporate. So the weight your wheelbarrow carries going in is the weight the demo crew carries coming out. Specialty mixes differ: lightweight structural concrete (expanded shale aggregate) runs 105-115 lb/cu ft, and lightweight cellular fill can drop to 30-60, but nothing in a residential driveway or patio is lightweight mix.
Worked Example 1: Slab Weight
The slab formula: length (ft) x width (ft) x thickness (inches) x 12.5 = weight in pounds.
- 10×10 patio, 4 inches thick: 100 sq ft x 4 x 12.5 = 5,000 lb — 2.5 tons
- 16×20 driveway pad, 4 inches: 320 x 4 x 12.5 = 16,000 lb — 8 tons
- Standard sidewalk square (5×5, 4 in): 25 x 4 x 12.5 = 1,250 lb per square
- 24×24 garage slab, 6 inches: 576 x 6 x 12.5 = 43,200 lb — over 21 tons
Thickness is the estimate-killer in demolition. Plenty of “4-inch” driveways were poured 5 to 6 inches thick at the edges or over old concrete, adding 25-50% to the tonnage. Before pricing disposal, drill or break a test spot and measure. Note that these figures cover weight only — if you’re still at the planning stage figuring volume for a pour, run the yardage math in our guide to how much concrete do I need first, then convert to weight here.
Worked Example 2: Bag Math
Bagged concrete is labeled by dry weight, and the yield is printed on the bag:
- 80 lb bag: yields 0.60 cu ft — cured weight of that concrete about 90 lb (dry mix + mixing water retained in the cure)
- 60 lb bag: yields 0.45 cu ft — about 68 lb in place
- 50 lb bag: yields 0.375 cu ft — about 56 lb in place
Two practical consequences. First, transport: a half pallet of 80 lb bags (21 bags) weighs 1,680 pounds — already past the payload of many half-ton pickups once you add a driver and tools. A full 42-bag pallet at 3,360 pounds belongs on a 3/4-ton truck or a delivery flatbed, full stop. Second, project scale: it takes 45 of the 80 lb bags to make one cubic yard, which is why bag math stops making sense past about a yard — the counts, the mixing labor, and roughly $270-$360 per yard in bag costs all argue for ready-mix. Our breakdown of how many bags of concrete in a yard runs that crossover math in detail.
Worked Example 3: Yards and Truck Loads
Ready-mix arrives in trucks carrying 8 to 10 cubic yards — 32,400 to 40,500 pounds of concrete on a vehicle that grosses 60,000-70,000 pounds loaded. That’s why drivers refuse to leave the street or a reinforced apron: a loaded mixer will crack a residential driveway (rated for maybe 8,000-pound vehicles) and can crush septic tanks, buried pipe, and irrigation lines. If the pour is more than about 20 feet from where the truck can safely park, the weight math is exactly what forces the decision toward pumping or a long chute session.
For smaller quantities: a 1-yard towable mixer trailer loaded weighs around 7,000 pounds combined — check your hitch and truck ratings before the batch plant loads you.
Demolition Weight: Dumpsters and Disposal
Broken concrete is where homeowners get burned, because dumpster pricing is weight-based and concrete maxes out containers long before it fills them. Rule of thumb for rubble: broken concrete with voids still averages about 2,000-2,400 lb per cubic yard of loose debris.
- A 10-yard dumpster typically carries a 10-ton weight limit for clean concrete — that’s the demolished 16×20 driveway from the example above, with margin
- Never order a 30- or 40-yard box for concrete; you’d hit the weight limit with the container a quarter full, and many haulers prohibit it outright
- Ask for a clean concrete load: rubble with no trash mixed in often gets a flat rate ($300-$550 in most markets) because the hauler recycles it as crushed aggregate
- Overage fees run $65-$125 per ton past the limit — a 20% thickness surprise on a driveway is a $200-$400 line item
Loading matters too: fill dumpsters with concrete only halfway up the walls and distribute evenly, or the roll-off truck may legally refuse the pickup.
Structural Loading: When Slab Weight Sits on Something
Concrete on grade pushes on dirt and nobody cares. Concrete on a structure is another story. A 4-inch slab imposes a 50 lb/sq ft dead load — residential floor framing is typically designed for 40 lb/sq ft live load plus 10-15 dead, so pouring even a thin slab or heavy overlay over a framed floor requires an engineer, not optimism. Common flashpoints: concrete countertops (a 2-inch-thick, 2-foot-deep run weighs 25 lb per linear foot — standard cabinets handle it, but check leveling feet), hot tub pads on decks, and mortar beds under tile upstairs. When in doubt, weigh it on paper first; the formula is the same 12.5 lb per square foot per inch everywhere.
Hauling It Yourself: Vehicle Payload Reality
The most dangerous place for bad concrete-weight math is your own truck bed. Payload ratings — the yellow door-jamb sticker, not the marketing tow number — run about 1,400-1,900 pounds for a typical half-ton pickup, 2,200-3,000 for a three-quarter-ton, and roughly 1,100 for a compact truck. Translate that to rubble: a half-ton legally carries about 10-12 square feet of broken 4-inch slab per trip once you subtract driver and tools. A single heaped bed of concrete chunks can easily hit 4,000 pounds, which is why the classic weekend scene — a sagging F-150 crawling to the dump — costs people axles, brakes, and tickets. Trailers help but have their own ratings: a common 5×8 utility trailer is rated 2,000-2,900 pounds gross, meaning one yard of rubble overloads most of them too. Price a 10-yard dumpster against eight white-knuckle dump runs and the container usually wins on both money and Saturday hours.
Quick Reference Table
- 1 cu ft: 150 lb
- 1 cu yd: 4,050 lb (2 tons)
- 1 sq ft at 4 in: 50 lb
- 1 sq ft at 6 in: 75 lb
- 80 lb bag, placed: ~90 lb over 0.6 cu ft
- Full mixer truck (10 yd): ~40,500 lb of product
- 10x10x4 in slab: 5,000 lb
Bottom Line
You don’t need an online tool once you own the constants: 150 per cubic foot, 4,050 per yard, 12.5 per square foot per inch. Run the multiplication before you rent the dumpster, load the truck, or promise your neighbor you’ll haul his old sidewalk to the dump in one trip. Concrete forgives sloppy finishing far more readily than it forgives sloppy weight math — the first costs you looks, the second costs you an axle.
