Ask any estimator the weight of concrete per cubic foot and you will get the same answer I learned my first week on a crew: 150 pounds. That round number — the standard weight of concrete per cubic foot for normal reinforced mixes — is what engineers plug into load calculations, what drives your demo-dumpster math, and what tells you whether a floor can carry a planter or a truck can carry your tear-out. But the honest range runs from under 30 lb for insulating foamed mixes to over 300 lb for shielding concrete, so the real skill is knowing which number applies.
- Why 150 lb Is the Standard Number
- Weight Chart by Concrete Type
- Worked Example 1: A Patio Slab
- Worked Example 2: Footings and Piers
- Worked Example 3: Countertops and Floors Over Framing
- Lightweight Concrete: When Less Weight Wins
- Quick Conversions and Rules of Thumb
- Estimating Demolition Weight Before You Book the Dumpster
- Where the Weight Number Bites You
Why 150 lb Is the Standard Number
Normal-weight concrete is roughly 70% to 80% aggregate (crushed stone and sand) by weight, and typical quartz or limestone aggregate has a specific gravity around 2.6 to 2.7. Mix that with cement paste and water and cured plain concrete lands at about 145 lb per cubic foot. Add typical rebar — steel weighs 490 lb per cubic foot, and reinforced structural members carry roughly 1% to 2% steel by volume — and the design community rounds to 150 lb per cubic foot (ACI’s long-standing convention for reinforced normal-weight concrete). In metric, that is about 2,400 kg per cubic meter. Two related figures worth memorizing: 150 lb/cu ft × 27 cu ft = 4,050 lb per cubic yard (call it two tons per yard), and a single 80 lb bag of concrete mix yields about 0.60 cu ft.
Weight Chart by Concrete Type
Pounds per cubic foot for the mixes you will actually encounter:
- Plain (unreinforced) normal-weight concrete: 145 lb
- Reinforced normal-weight concrete: 150 lb
- Structural lightweight concrete (expanded shale/clay aggregate): 90 to 115 lb
- Lightweight insulating concrete (perlite/vermiculite): 15 to 50 lb
- Cellular/foamed concrete: 20 to 60 lb
- Gypsum concrete floor underlayment (Gyp-Crete type): 105 to 115 lb
- Asphalt concrete (for comparison): about 140 lb
- Heavyweight concrete (magnetite/barite aggregate, radiation shielding): 190 to 380 lb
- Fresh (wet) normal concrete in the wheelbarrow: 150 to 155 lb
Note the wet-versus-cured myth: concrete barely changes weight as it cures. Hydration binds most of the mix water chemically; only a few pounds per cubic foot of bleed and evaporative water leave. Plan formwork and equipment for the wet weight — it is essentially the same as the final weight.
Worked Example 1: A Patio Slab
A 12 x 14-foot patio at 4 inches thick. Volume first: 12 × 14 = 168 sq ft; 4 inches = 0.333 ft; 168 × 0.333 = 56 cu ft, or 2.07 cubic yards. Weight: 56 × 150 = 8,400 lb — over four tons sitting in your backyard. That number matters twice: ordering (you would call the plant for 2.25 yards to cover spillage and grade variation) and demolition (an 8,400 lb tear-out fills most of a 10-yard dumpster’s 2 to 4-ton weight allowance, so confirm the tonnage cap before booking).
Worked Example 2: Footings and Piers
Cylindrical volumes trip people up, so here is the pattern. A 12-inch-diameter Sonotube pier 42 inches deep: radius 0.5 ft, so volume = 3.1416 × 0.5² × 3.5 ft = 2.75 cu ft. Weight = 2.75 × 150 = 412 lb, which is about five 80 lb bags of mix per pier (2.75 ÷ 0.60 = 4.6 bags). Ten deck piers = 4,120 lb of concrete — worth knowing when you are deciding between 46 hand-mixed bags and a short-load ready-mix delivery. A continuous footing 16 inches wide × 8 inches deep × 40 feet long is 35.5 cu ft (16/12 × 8/12 × 40), weighing 5,330 lb, or 1.32 cubic yards.
Worked Example 3: Countertops and Floors Over Framing
Anything concrete placed on wood framing needs a dead-load check. A 2-inch-thick concrete countertop weighs 150 ÷ 6 = 25 lb per square foot; a 10-foot run of 25.5-inch-deep counter is about 21 sq ft, so 525 lb — fine on cabinets, but the seam and overhang design has to carry it. A 1.5-inch gypsum-concrete pour over subfloor (common over radiant tubing) at 110 lb/cu ft adds 110 × 0.125 = 13.75 lb per sq ft, which is why installers verify the joists were designed for a 15 psf dead load before pumping. Quick per-inch cheat: every 1 inch of normal-weight concrete = 12.5 lb per square foot.
Lightweight Concrete: When Less Weight Wins
Structural lightweight concrete swaps stone for kiln-expanded shale, clay, or slate and lands around 110 lb per cubic foot while still reaching 3,000 to 5,000 psi. That 25% to 30% weight saving is why high-rise decks, elevated pool surrounds, and pan-deck floors spec it despite a 20% to 40% price premium (figure $130 to $180 per yard versus $110 to $160 for normal mix, market depending). Insulating cellular and perlite mixes go far lighter — down to 20 to 50 lb per cubic foot — but at compressive strengths of 100 to 1,000 psi they are fill and insulation, not structure. If you are patching or topping an elevated slab, matching the original density matters; drop a normal-weight topping on a lightweight deck and you have quietly added dead load the engineer never approved.
Quick Conversions and Rules of Thumb
The numbers I use without a calculator:
- 1 cubic yard = 27 cubic feet = about 4,050 lb (2 tons) of normal concrete
- 1 cubic foot = 150 lb reinforced, 145 plain; call it 12.5 lb per sq ft per inch of thickness
- 4-inch slab = 50 lb per sq ft; 6-inch slab = 75 lb per sq ft
- 80 lb bag = 0.60 cu ft yield → 45 bags per cubic yard; 60 lb bag = 0.45 cu ft → 60 bags per yard
- Full 10-yard mixer truck = about 40,000 lb of concrete plus a 27,000 lb truck — nearly 70,000 lb on your driveway, which is why drivers stay on the street
- Metric: 2,400 kg/m³ normal weight; 1,750 to 1,850 kg/m³ structural lightweight
Estimating Demolition Weight Before You Book the Dumpster
Tear-out estimating deserves its own worked pass because it is where homeowners most often get the math wrong. Broken concrete does not weigh less than intact concrete per solid cubic foot, but rubble bulks up: a demolished slab occupies roughly 1.4 to 1.6 times its original volume once broken and loosely piled, even though the tonnage stays the same. So estimate weight from the intact dimensions, and estimate container space from the bulked volume. Example: removing a 10 x 20-foot, 4-inch walkway. Intact volume is 66.7 cu ft; weight is 66.7 × 145 (older plain concrete) = about 9,700 lb, or 4.85 tons. Bulked, that rubble fills roughly 95 to 105 cu ft — 3.7 cubic yards of container space. The booking mistake: a 20-yard dumpster has plenty of room but usually a 3-ton cap, so this job wants either two hauls or a dedicated 10-yard “heavy debris” box, which most companies rate for 8 to 10 tons precisely because concrete maxes weight first. Recyclers change the economics: many concrete crushing yards accept clean broken concrete (no rebar tangles, no soil) for $10 to $30 per ton or occasionally free, versus $60 to $110 per ton in a mixed-debris container. Separating your rubble can cut disposal costs by two-thirds on a driveway-scale demo.
Where the Weight Number Bites You
Three field scenarios where this math saves real money. Demolition hauling: dumpster companies price by the ton, and concrete maxes out weight long before volume — a 20-yard container might allow 3 tons, which is just 40 sq ft of 6-inch driveway per ton removed; order the low-boy concrete-only box instead. Equipment limits: a half-yard of wet mix in a tow-behind mixer is 2,000 lb before the mixer’s own weight, past the rating of many light-duty hitches. And structural add-ons: setting a 24 x 24 x 2-inch concrete paver path (each paver 100 lb) across a septic tank lid, or parking a 4,000 lb pallet of bagged mix on an old porch slab, are both mistakes I have watched happen. When in doubt, run the cubic feet, multiply by 150, and respect the answer.
