Size to Weight Calculator — Rectangular Cuboid
Enter the length, width and height of a rectangular block, choose the material (concrete, steel, wood, and more), and get the weight in kg, g, lb and oz.
m
m
m
Material
Weight of the rectangular cuboid at the selected material density
360 kg
- 1
Volume
1 × 0.5 × 0.3 = 0.15 m³Length × width × height (all in metres). - 2
Mass
0.15 m³ × 2,400 kg/m³ = 360
How does this calculator work?
The mass of a rectangular cuboid is length × width × height × density. Enter dimensions in metres and choose a material from the preset list (steel 7,850 kg/m³, concrete 2,400 kg/m³, oak 700 kg/m³, etc.) or enter a custom density. Mass is returned in kg, g, lb and oz.
Formula
How this is calculated
The weight (more precisely, mass) of a rectangular cuboid is simply its volume multiplied by the material density: Mass = L × W × H × ρ. All three dimensions are entered in metres and the density is in kg/m³, giving mass in kilograms. The calculator then converts to grams (kg × 1000), pounds (kg × 2.20462), and ounces (kg × 35.274).
The preset material densities are standard reference values: for example, steel is 7,850 kg/m³, concrete 2,400 kg/m³, and oak wood 700 kg/m³. Real materials vary with grade, moisture content, and composition — a dry structural-grade concrete may be 2,300–2,500 kg/m³ while a dense aggregate concrete can reach 2,800 kg/m³. Use the "custom density" option if you have a measured or manufacturer-specified density.
This calculator assumes a solid, homogeneous block of uniform density — hollow objects, composite materials, or irregular voids will give a higher-than-actual result. Dimensional accuracy matters: an error of 1% in each dimension compounds to roughly 3% error in volume and therefore in mass.
Frequently asked questions
Multiply by 1,000. Water has a density of 1 g/cm³ = 1,000 kg/m³. Steel at 7.85 g/cm³ is 7,850 kg/m³. You can also enter the custom density directly in kg/m³ using the custom option.
Technically, mass (in kg) is the amount of matter, while weight is the gravitational force (in Newtons = kg × 9.81 m/s²). In everyday use the two are used interchangeably at sea level on Earth, which is the context of this calculator.
For irregular shapes, calculate the volume separately (e.g. using geometry or water displacement) then multiply by density. For objects with internal voids, estimate the void fraction and subtract it from the volume before calculating.
Also known as
TG we-Calculate Editorial Team. (2026). Size to Weight Calculator — Rectangular Cuboid [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/size-to-weight-rectangular-cuboid-calculator
TG we-Calculate Editorial Team. "Size to Weight Calculator — Rectangular Cuboid." TG we-Calculate. 2026. https://we-calculate.com/calculator/size-to-weight-rectangular-cuboid-calculator.
TG we-Calculate Editorial Team, "Size to Weight Calculator — Rectangular Cuboid," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/size-to-weight-rectangular-cuboid-calculator
@misc{wecalculate_size_to_weight_rectangular_cuboid_calculator, title = {Size to Weight Calculator — Rectangular Cuboid}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/size-to-weight-rectangular-cuboid-calculator}}, year = {2026}, note = {TG we-Calculate} }
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