Concrete Weight Calculator — lb, Tons and kg

Ordinary concrete runs about 150 lb per cubic foot. Multiply by 27 and the weight of concrete per cubic yard comes to 4,050 lb, which is just over 2 US tons. Everything else on this page is a variation on that one figure. Aggregate, cement and water set it, so a rich, dense mix lands a little above and a lean, airy one a little below, but 150 is the number engineers and suppliers reach for when nothing more specific is known.

For a flat pour the figure that matters is weight per square foot, because that is what the ground or the framing underneath actually feels. It is just the thickness in inches divided by 12, times 150. A 4 in slab is 50 lb per square foot, a 6 in slab is 75, and an 8 in slab is 100. The first table above lays these out so you can read across to any area.

You need a volume before you can weigh anything, and if all you have is a set of dimensions, the concrete volume calculator turns them into cubic feet and cubic yards first. A worked example: a 10 × 12 ft slab at 4 in is 120 × 4 ÷ 12 = 40 cubic feet, so it weighs 40 × 150 = 6,000 lb. That is 3 US tons, or 2,722 kg, and it is the same as 50 lb per square foot across 120 square feet.

Weight becomes a decision when something has to carry it. Residential framing is typically designed for around 40 lb per square foot of live load, with roughly 10 lb per square foot left over for permanent dead load such as flooring and finishes. A 4 in slab at 50 lb per square foot is five times that spare allowance before anyone has stood on it. That is why pouring concrete over a deck, a balcony or an upper floor is a question for a structural engineer, who can check the joists, beams, posts and footings. The floor load check compares two numbers and raises that question. It does not tell you a floor is safe.

Steel changes the figure less than people expect. Rebar weighs about 490 lb per cubic foot, but at 1 to 2 percent of the volume it lifts the average by only a few pounds, so reinforced concrete is usually taken as about 156 lb per cubic foot. Moisture moves it the other way. Concrete gives up a small amount of mixing water as it cures, so a hardened slab can be a few percent lighter than it was at the pour. For hauling and for floor load, use the higher fresh figure, since that is what you carry and what the framing sees first. The same goes for ready mix concrete weight on a delivery ticket, which is quoted wet.

Haulage is where the numbers surprise people. A single cubic yard at 4,050 lb is more than twice a half-ton pickup's typical payload, so it overloads the truck on its own, and the bed looks nearly empty while the springs say otherwise. A tandem-axle trailer carries about 7,000 lb, or under 2 cubic yards. Anything bigger is a delivery. The haulage select shows how many trips a load needs for the vehicle you pick.

Walls add their own sums. A block wall's weight comes from the published weight of each unit, and the concrete block wall calculator will count the blocks and add core fill, which matters because solid grout can double the figure. Enter the block count on the Block wall tab for the unfilled weight.

Finally, units. Most of the world works in kilograms and cubic metres, where normal concrete is about 2,400 kg per cubic metre, the same density as 150 lb per cubic foot. If a supplier quotes in tonnes and your plans are in pounds, a pounds to kilograms and tonnes converter settles it. One metric tonne is 2,204.62 lb, which is not the same as a US ton of 2,000 lb, and mixing the two up is a 10 percent error on a big load.