What this calculator does
Concrete weight follows the same simple relationship as any solid slab: volume multiplied by density. For a rectangular pour, volume is length times width times thickness, and multiplying that by the density of the concrete mix gives the total weight, whether you are checking what a slab will bear on the ground below or estimating a load for transport.
Density is not a single fixed number. Normal-weight concrete is commonly cited around 2400 kg per cubic metre, but lightweight and heavyweight mixes, added aggregates, and reinforcement all shift that figure, so this calculator treats density as an input you set rather than a number baked in behind the scenes.
The formula
Convert length, width and thickness to metres, multiply them together for the volume in cubic metres, then multiply by the density in kilograms per cubic metre to get the weight in kilograms.
| Term | Meaning |
|---|---|
| Density | Mass per unit volume of the concrete mix, in kilograms per cubic metre. Normal-weight concrete is commonly around 2400 kg/m³, but this varies by mix. |
| Volume | Length × width × thickness, expressed in cubic metres. |
| Unit weight of concrete | Another name for its density: the weight of one cubic metre of the set material. |
The inputs explained
| Field | What to enter |
|---|---|
| Length (m) | The length of the slab, footing or pour. |
| Width (m) | The width of the slab, footing or pour. |
| Thickness (mm) | The thickness (depth) of the pour, usually much smaller than length or width, entered in millimetres. |
| Density (normal-weight concrete ≈ 2400 kg/m³, edit for other mixes) (kg/m³) | The density of the specific concrete mix being used. Adjust from the 2400 kg/m³ default for lightweight, heavyweight, or reinforced concrete. |
When to use it
Checking a slab load before it is poured
Knowing the weight of a proposed slab ahead of time is part of checking whether the ground, formwork or supporting structure beneath it is rated to carry it.
Estimating transport or crane requirements for precast pieces
A precast concrete block or panel's weight, from its own dimensions and density, is what determines whether a given crane, truck or lifting gear can handle it.
Comparing standard and lightweight mixes
Switching the density input between a normal-weight and a lightweight mix, for the same slab dimensions, shows directly how much weight a lighter mix actually saves.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How does slab weight change with thickness?
A fixed 3 m by 2 m slab area, across a range of pour thicknesses.
| Thickness | Weight | In tonnes |
|---|---|---|
| 75 mm | 1,080 kg | 1.080 t |
| 100 mm | 1,440 kg | 1.440 t |
| 125 mm | 1,800 kg | 1.800 t |
| 150 mm | 2,160 kg | 2.160 t |
| 200 mm | 2,880 kg | 2.880 t |
| 250 mm | 3,600 kg | 3.600 t |
How does weight per square metre change with the concrete mix's density?
A fixed 1 square metre area at 100 mm thickness, across a range of mix densities.
| Density | Weight | In tonnes |
|---|---|---|
| 1,800 kg/m³ | 180 kg | 0.180 t |
| 2,000 kg/m³ | 200 kg | 0.200 t |
| 2,200 kg/m³ | 220 kg | 0.220 t |
| 2,400 kg/m³ | 240 kg | 0.240 t |
| 2,500 kg/m³ | 250 kg | 0.250 t |
| 2,700 kg/m³ | 270 kg | 0.270 t |
Questions
What is the unit weight of concrete?
It is the same thing as density, usually stated in kilograms per cubic metre. Normal-weight concrete is commonly cited around 2400 kg/m³, though the exact figure depends on the aggregate and mix used, and should be checked against the specific mix design where accuracy matters.
How much does a concrete block weigh?
A precast block's weight follows the same length × width × thickness × density calculation as a poured slab, using the block's own dimensions. Enter its actual dimensions and the density of the mix it was cast from to get a specific figure rather than a generic one.
Does reinforcement (rebar) change the weight significantly?
Steel reinforcement is considerably denser than concrete, so a heavily reinforced element weighs somewhat more than the plain concrete-only figure. For a rough estimate the plain-concrete weight is usually close enough; for a precise figure, add the estimated weight of the steel separately.
Why is concrete density given as a range rather than one number?
The aggregate used, air content, water-cement ratio and any additives all affect the set density, so published figures for "normal-weight concrete" span a range rather than landing on one exact value. Using the actual mix design's stated density gives a more accurate weight than a generic assumption.
The same volume-times-density approach is used in the steel plate weight calculator and the glass weight calculator, for a metal plate or a glass pane instead of a concrete pour.