Size to Weight Calculator (Rectangular Cuboid)
Calculate the weight of any rectangular box or cuboid from its length, width and height, using a built-in materials density table or your own value.
Size to Weight Calculator: Rectangular Cuboid Weight from Dimensions
If you have a rectangular block, box, slab, or crate and need its weight but don't have a scale handy, this calculator gets you there from three measurements and one material property: length x width x height x density = weight. Pick a built-in density preset (water, mild steel, iron, aluminum, copper, glass, brick, concrete, or softwood/hardwood lumber) or type in a custom density in kg/m3 for anything else, and the calculator handles the geometry and unit conversion for you.
This is the generalist tool in this site's weight-calculator family: it works for any rectangular cuboid regardless of material. If you work with one material all the time, the dedicated metal weight, steel weight, or concrete weight calculators carry deeper, grade-specific density tables for that material alone.
How to use the size to weight calculator
- Enter the length, width, and height of the block, choosing whichever unit suits your tape measure (mm, cm, m, in, or ft).
- Choose a material preset from the density list, or switch to a custom density and type in a figure (in kg/m3) from a datasheet or reference table.
- Set the quantity if you are weighing more than one identical block.
- Choose your output mass unit (kg, g, lb, or oz) and read off the weight per piece and the total weight.
The math behind the calculation
Weight = volume x density, and volume for a rectangular cuboid is simply length x width x height. The geometry never changes — swapping the density is all it takes to move between materials.
Worked example: a solid block 0.4 m long, 0.4 m wide, and 0.4 m tall, made of iron (density 7,874 kg/m3). Volume = 0.4 x 0.4 x 0.4 = 0.064 m3. Weight = 0.064 x 7,874 ~ 503.9 kg. Swap the same 0.064 m3 block to common brick (density 2,400 kg/m3) instead and the weight drops to 153.6 kg — same dimensions, very different weight, purely from the density used.
Pro tips
Because this calculator covers any material from water to gold, there's no single price-per-kg figure to quote generically. If you need a tradesperson to assess an item's weight or load on site without a scale, a typical Gibraltar callout for that kind of quick estimate runs around £28-£70.
- Measure the block's true outer dimensions, not a nominal or advertised size — a small error on any one of the three edges compounds because volume multiplies all three together.
