Size to Weight Calculator (Rectangular Box)

Created by Mateusz Mucha
Reviewed by Jack Bowater
Last updated: Jan 30, 2023

Table of contents:

This size to weight calculator lets you determine how much a rectangular box (e.g., a brick, book, door, companion cube, etc.) weighs based on size and density. It can also find an object's density provided you know its volume and weight. For example, if you have a brick with dimensions of 92 × 57 × 203 millimeters and a density of 2.4 kg/L, you'd find out that the weight of that object is 2.555 kg.

Our volume calculator and density calculator deal with problems related to this. The concrete calculator lets you calculate how many bags of concrete you need, while the brick calculator answers the question: how many bricks do I need?.


How do I find the weight of a box without a scale?

To find the weight of a box without a scale, you can use the relationship between mass and volume: mass = density × volume.

  1. Start by measuring the dimensions of the box.

  2. Find the box's volume by multiplying the three sides' lengths.

  3. Estimate or find the density of the material of interest.

  4. Make sure that the units agree (for example, use cubic meters for the volume and kilograms per cubic meter for the density), and calculate the mass using:
    mass = density × volume.

What is the weight of a cube of iron with side 40 cm?

The cube weighs approximately 504 kg. To find this result:

  1. Calculate the volume of the cube:

    V = l × l × l = 0.4 × 0.4 × 0.4 = 0.064 m³

  2. Identify the density of iron: d = 7874 kg/m³.

  3. Find the mass using:
    mass = density × volume = 7874 kg/m³ × 0.064 m³ = 503.94 kg

A cube with a side of 40 cm of iron weighs more than half a ton!

How do I convert from volume to weight?

To convert from volume to weight, you need to know the density of the material you're working with. The density is a measure of the mass of a known volume: the higher the density, the higher the weight of an object of fixed size. You can find the density of many materials online or measure it yourself from a sample.

Is weight proportional to size?

Yes, weight and size are proportional — at least if you consider the same material. The constant of proportionality is known as density, a property of matter that characterizes the weight of a given volume.

Mateusz Mucha
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