Concrete weight calculator

The weight of a slab or pour in pounds, kilograms, and tons — plus two numbers the other calculators leave out: the dead load per square foot for whatever holds the slab up, and the dry-bag weight you would actually haul.

01 How the math works

Weight is volume times density. Normal-weight ready-mix concrete runs 145 lb/ft³ (2,323 kg/m³), the ACI 318 estimating figure, so a cubic yard weighs 3,915 lb (1,776 kg). Give the calculator a volume — from slab dimensions or entered straight — and it multiplies through to pounds, kilograms, and tons.

The distributed dead load is the same weight spread over the floor area the slab sits on. For a slab of uniform thickness the area cancels, so the load per square foot depends only on thickness: thickness (ft) × 145. A 4 in slab is 48.3 lb/ft² whether it is 10 ft square or 100. That is the number a deck or floor frame is designed around, not the total pounds.

02 Worked example

Take the backyard patio slab: 10 ft × 12 ft × 4 in (3.05 m × 3.66 m × 100 mm). That is 40 ft³, or 1.48 yd³ (1.13 m³).

Weight: 40 × 145 = 5,800 lb (2,631 kg), which is 2.9 US tons (2.63 tonnes). Spread over the 120 ft² footprint, the dead load is 48.3 lb/ft² (236 kg/m²) — the figure that matters if that slab is a topping over a framed floor rather than sitting on grade.

Poured from bags instead, the same 40 ft³ takes 67 bags of 80 lb premix (40 ÷ 0.60, rounded up) — 5,360 lb of dry mix to haul home and carry to the form. The finished slab weighs 5,800 lb; the extra 440-odd pounds is the mix water going in on site.

03 When this calculator is wrong

The weight uses the 145 lb/ft³ normal-weight density. That is the right number for standard structural and flatwork concrete, and it is what governs a delivery ticket or a load rating. Two cases change it.

• Lightweight and specialty mixes weigh less. Structural lightweight concrete, made with expanded-shale or slag aggregate, is meaningfully lighter than 145 lb/ft³ — enough that a roof deck or long-span floor is often specified in it precisely to cut dead load. If your mix is not standard normal-weight, use the density on the supplier's mix design, not this default.
• Fresh, cured, and reinforced weights differ. The 145 lb/ft³ figure is the in-place structural value. Freshly placed concrete carries free mix water it later loses to hydration and evaporation, and a heavily reinforced footing adds the steel's weight on top of the concrete. For residential slabs the rebar is under 0.5% of volume and the difference is in the noise; for a load-rated pour, weigh the ticket, not the calculator.
• Total pounds is not what a truck bed cares about. A single cubic yard is 3,915 lb — more than a half-ton pickup's namesake 1,000 lb payload rating, and past the real payload of most light-duty trucks. The volume of a yard fits in an 8 ft bed; the weight does not. Split the load or have it delivered.

04 What to do with the result

For hauling, work backward from the vehicle. Take the payload rating off the door jamb, divide the total weight by it, and that is how many trips — or the size of trailer — the pour needs. A yard of ready-mix at 3,915 lb is a delivery, not a pickup load; bagged, the same yard is 3,600 lb of dry mix (45 × 80 lb) you can split across trips.

For structural planning, hand the dead load in lb/ft² to whoever sizes the joists or beam. A framed floor is designed for a live load plus the dead load of everything permanently on it; the residential live load in the IRC joist tables is 40 psf, and a 4 in concrete topping adds 48.3 psf of dead load on its own — more than the live load itself. That is not a DIY sizing decision. It is the number the person who does the sizing needs first.

05 Common questions

How much does a yard of concrete weigh?

A cubic yard of standard normal-weight ready-mix weighs about 3,915 lb (1,776 kg) — just under 2 US tons. That is the ACI/NRMCA figure for a 4000 psi mix and the number to use for delivery and load planning.

How much does a cubic foot of concrete weigh?

145 lb (about 65.8 kg) for normal-weight concrete, which is 2,323 kg/m³ in metric. Multiply cubic feet by 145 to get pounds; that single factor is the whole calculator.

How much does a 4 inch slab weigh per square foot?

48.3 lb/ft² (236 kg/m²). Thickness in feet times 145: a 4 in slab is (4 ÷ 12) × 145. A 6 in slab is 72.5 lb/ft². This is the dead load a supporting frame carries, independent of the slab's length and width.

Can I haul concrete in a pickup truck?

By weight, barely. A single cubic yard is 3,915 lb finished, or 3,600 lb as dry 80 lb bags — both above the payload of a typical light-duty pickup even though the volume fits in the bed. Split it into part-yard loads sized to the truck's rating, or have ready-mix delivered.