Formula
Volume is length times width times thickness, or the cylinder π times radius squared times height. Weight is that volume times the density. 150 pounds per cubic foot times 27 is 4,050 pounds per cubic yard. One pound per cubic foot is 16.01846 kilograms per cubic metre, so 150 is about 2,403. The metric preset uses 2,400 kilograms per cubic metre, the rounded companion, and the tests say so.
weight = volume × density
4 in slab = 50 lb/ft² at 150 lb/ft³
finished bag ≈ yield × density
Normal-weight concrete is about that dense because of the stone, the sand, the cement, and the water. Air and a lighter aggregate move it. Structural lightweight concrete is quoted at an equilibrium density usually from 90 to 115 pounds per cubic foot. This page uses the midpoint, 102.5, and says so. Heavyweight shielding concrete is left off. The figure is the usual normal-weight density, not a claim that fresh concrete is a few pounds heavier than the hardened number. A bag’s dry weight is lower than the finished weight because the yield is the wet volume. A truck, a trailer, a floor, and a hoist have their own ratings.
Worked examples
10 × 10 ft × 4 in. 33.33 cubic feet, 1.23 cubic yards, 5,000 pounds, 50 pounds per square foot.
One cubic yard. 4,050 pounds. A 20 × 2 × 1 ft footing. 6,000 pounds. A 12 in column, 8 ft tall. 942 pounds.
5 × 4 × 0.1 m at 2,400 kg/m³. 4,800 kilograms, 10,582 pounds. 20,250 pounds is 5.0 cubic yards at 150 pounds per cubic foot.
Reference
Common slab thicknesses at 150 pounds per cubic foot: 4 in is 50 lb/ft², 5 in is 62.5, 6 in is 75.
Questions
How much does a cubic yard of concrete weigh?
At 150 pounds per cubic foot, 27 cubic feet weigh 4,050 pounds, 2.025 short tons, about 1,837 kilograms. That 150 is the figure used when you do not have a test.
How much does a cubic foot of concrete weigh?
About 150 pounds for normal-weight concrete. The Portland Cement Association puts freshly mixed normal-weight concrete at 140 to 150 pounds per cubic foot. Lightweight concrete is a different material.
How much does a 4-inch slab weigh per square foot?
Four inches is one third of a foot. At 150 pounds per cubic foot that is 50 pounds per square foot. Five inches is 62.5, and six inches is 75, at the same density.
How much does an 80 pound bag of concrete weigh when mixed?
The dry bag is 80 pounds. The finished volume on the Quikrete sheet used here is 0.60 cubic feet, which at 150 pounds per cubic foot is about 90 pounds, because the mix water is in the finished concrete. The yield on your bag wins.
How much does a concrete slab weigh?
Length times width times thickness, in feet, times the density. A 10 by 10 foot slab at 4 inches is 5,000 pounds at 150 pounds per cubic foot.
How many cubic yards are in a ton of concrete?
One short ton is 2,000 pounds. At 150 pounds per cubic foot that is 0.4938 cubic yards. A metric tonne is a different 1,000 kilograms.
Is reinforced concrete heavier?
The steel is extra weight this page does not add. Rebar quantity is on the rebar calculator. The density here is the concrete itself.
Sources
- Portland Cement Association, Design and Control of Concrete Mixtures, Chapter 5. Freshly mixed normal-weight concrete is given as 140 to 150 pounds per cubic foot, 2,200 to 2,400 kilograms per cubic metre.
- ACI 318, as quoted in the Expanded Shale, Clay and Slate Institute’s summary of the code: when a test is not available, the density of normal-weight concrete is taken as 150 pounds per cubic foot, 2,400 kilograms per cubic metre. The 2,400 figure on the metric preset is that rounded companion.
- ACI 213, as quoted by ESCSI: structural lightweight concrete usually has an equilibrium density from 90 to 115 pounds per cubic foot. The lightweight preset is the midpoint, 102.5. It is not a mix design.
- Bag yields: Quikrete Concrete Mix data sheet 1101, the same yields the concrete calculator uses. 40 lb is 0.30 cubic feet, 50 lb is 0.375, 60 lb is 0.45, 80 lb is 0.60. The bag in your hand wins.