Concrete Weight Calculator

Background.

A cubic metre of ordinary concrete weighs about 2.4 tonnes, more than a small car, and that catches people out at every stage of a job: the precast panel that turns out to be beyond the hired lifting gear, the trailer overloaded with broken slab, the floor asked to carry a heavy plinth. Knowing the mass before anything is lifted, hauled or supported is the whole point.

The arithmetic is short because concrete is close to uniform. Measure one rectangular piece, multiply its length, width and thickness to get cubic metres, multiply by the number of identical pieces, then by the density. The default of 2,400 kg/m³ is the metric counterpart of the nominal 150 lb/ft³ the American Concrete Institute uses for normal-weight concrete, the everyday kind made with natural sand, gravel or crushed stone.

One rule of thumb falls straight out of that density: each millimetre of thickness adds 2.4 kg to every square metre. A 100 mm slab weighs about 240 kg per square metre; a 150 mm slab about 360 kg. Scale that up to a 6 m by 4 m garage floor at 100 mm and the slab is 5,760 kg — nearly six tonnes resting on the ground beneath it.

For anything that will be lifted, the mass worked out here is where the plan starts, not where it ends. The crane or hoist also carries the slings, shackles and any spreader beam, and a precast unit being stripped from its casting bed can cling to the form and briefly pull harder than its own weight, so erectors build allowances on top of the dead mass. For anything that will be hauled, the useful comparison is with the vehicle's payload in kilograms; a trailer can be over its limit long before it looks full.

The density box is editable because real concrete varies. Steel reinforcement is more than three times as dense as concrete, so heavily reinforced members run heavier. Mixes made with expanded clay, shale or other lightweight aggregates run much lighter, and freshly placed concrete still holds water that later dries out. If a mix design or supplier data sheet gives a density, use that figure. Every piece is also treated as a solid block, so hollow blocks, cored planks and panels with openings will come out heavier than they really are unless you take the voids off the dimensions first.

What is concrete weight calculator?

Concrete weight, as worked out here, is the mass of one or more solid rectangular concrete pieces: their combined volume multiplied by the density of the mix. Density is mass per unit volume, in kilograms per cubic metre; American practice often calls the same quantity unit weight and quotes it in pounds per cubic foot. Strictly, kilograms and pounds measure mass, and the force a slab presses onto its supports is that mass times gravity, but on site the figure in kg or lb is what everyone means by weight. Normal-weight concrete is concrete made with ordinary dense aggregates rather than lightweight or extra-heavy ones. Even within that family, density belongs to a particular mix in a particular state rather than to concrete in general: the rock used as aggregate, the share of air bubbles and the water still held in the pores all move it. Air is the easiest of these to reason about, because it has next to no mass — each extra percentage point of air by volume takes roughly 1% off the density, so a mix carrying five points more air than the default is closer to 2,280 kg/m³ than 2,400.

How to use this calculator.

1. 01Measure one piece and enter its length, width and thickness in metres. Divide millimetres by 1,000: a 100 mm slab is 0.1 m thick, and the 0.01 m default is just 10 mm.
2. 02Measure the thickness at several points rather than trusting the drawing. Slabs poured on uneven ground are often thicker than specified, and the average of your readings is the figure to enter.
3. 03Enter how many identical pieces there are. If the pieces differ in size, run each size separately and add the masses together.
4. 04Keep 2,400 kg/m³ for ordinary concrete, or replace it with the density on the supplier's data sheet for lightweight, heavyweight or heavily reinforced work.
5. 05Read the total mass in kilograms or pounds, and use the total volume to check against the cubic metres ordered or delivered. For a lift, divide the total by the number of pieces: the crane or the people carrying it handle one piece at a time.

The formula.

Mass = length × width × thickness × quantity × density, or m = L × W × T × n × ρ. L, W and T are the dimensions of one piece in metres, so their product is that piece's volume in cubic metres; n is the number of identical pieces, and ρ (rho) is the density in kg/m³. The pound figure is the kilogram mass multiplied by 2.2046226218, the number of pounds in a kilogram. Every term is a straight multiplier, so a 10% error in any one of them becomes a 10% error in the mass. Thickness is the measurement most often wrong in practice: slabs are rarely poured perfectly level, and one specified at 100 mm that averages 110 mm is 10% heavier than planned. The 2,400 kg/m³ default rounds ACI's nominal 150 lb/ft³, which converts to about 2,403 kg/m³.

Three assumptions sit behind the short equation. Each piece is taken to be a solid rectangular block, so length times width times thickness is its true volume; cylinders, wedges and panels with openings need the workarounds in the questions below. The density is taken to be the same all the way through, which is close to true for plain concrete but less so for a beam with a dense cage of bars along one face. And the pieces are taken to be identical, so the quantity simply scales the result. None of the terms is a force: to get the load in newtons that an engineer works with, multiply the kilograms by 9.81 m/s², which turns the 216 kg of the worked example into about 2.12 kN.

A worked example.

Frequently asked questions.

References& sources.

1. [1]American Concrete Institute. ACI 318-19. Definition of normalweight concrete; nominal 150 lb/ft³. Retrieved 2026-08-06. access: gated.
2. [2]National Institute of Standards and Technology. NIST SI Guide, 2008 edition. Appendix B unit relationships. Retrieved 2026-08-06.
3. [3]International Code Council. 2021 International Residential Code. Building construction context. Retrieved 2026-08-06.
4. [4]U.S. Department of Agriculture Forest Products Laboratory. Wood Handbook 2021. Engineering materials and construction. Retrieved 2026-08-06.
5. [5]Occupational Safety and Health Administration. Construction standards current 2026. 29 CFR Part 1926 construction safety. Retrieved 2026-08-06.