We all know that the size of a package affects its weight. But what if you’re trying to calculate the weight of a rectangular box from its dimensions? Luckily, there’s an easy way to find out! We’ll walk through it together here.

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What is volume?

Volume, or volumetric measurement, is the process of measuring the space occupied by an object. Volume is often calculated using a container-based measurement system in which one container holds a known volume. In these systems, only the amount of liquid or gas inside a container can be measured; for example, in order to measure how much air is inside a balloon, you would need to use a pump because you can’t see through it. To clarify:

  • Weight is usually determined by placing an object on some sort of scale
  • Volume is usually determined by placing an object into a container with known dimensions and taking measurements, or by using Archimedes’s principle

The formula for the volume of a box

The formula for calculating the volume of a rectangular box is:

V = l \times w \times h

The length, width, and height dimensions must be in the same unit for the volume formula to work. The units are most often centimeters (cm), but can also be millimeters (mm), inches (in) or any other measurement for length. For example, if you have a rectangular box that measures 2″, 3″, 4″, then its volume is equal to 24 cubic inches.

The volume of an ideal cube (where no extra space exists between its sides) can be calculated by multiplying its edge length by itself three times:

V = a^3

Find the weight using volume and density

To find the weight of a rectangular box, you need to know two things: volume and density. The volume is how much space something takes up, and the density is how much it weighs per unit of volume. The simplest way to go about this would be to tell you to multiply these two values. To put it mathematically:

m = V \times \rho

m is the mass, V is the volume, and the Greek letter ρ (pronounced rho) is the density.

How to find the density of an object

The density of any object can be found by reverse-engineering the formulas from before. The simplest way is to take an object, find its volume and mass, and use the following formula to find its density:

\rho = \frac {m}{V}

If the object is made out of one type of material, you can simply find the density of that specific material online, or in a handbook.

How to use the size-to-weight calculator

The size-to-weight calculator combines the formulas we mentioned before. So, to start, you would enter the initial measurements of your container, the length, width, and height, which are going to be used to calculate the volume. Then, you will enter the density, which, combined with the volume, will allow the calculator to give you the final weight of the box.


Keeping the size of your packages in mind will help your shipping go more smoothly. If you’re using a carrier that doesn’t allow for weight pricing, you’ll likely have to pay for the package based on its actual weight. But if you need to ship a large package that’s very light, dimensional weight pricing could be an advantageous factor when choosing the right carrier or provider for your shipment. Either way, by keeping dimensions and weights in mind when shipping items, shippers can save themselves a ton of headaches and costs in the long run.


How do you find the weight of a rectangular box?

You can find the weight of a box by using the formula m = V * ρ. Alternatively, you could just put it on a scale and measure it that way.

How do you work out the capacity of a box?

The capacity of a box is equal to its volume. To calculate volume, you can use the formula V = l * w * h, those being the separate measurements of the box.

What is the density of an object?

The density of an object is a measurement that shows how much an object weighs per unit of volume. The standard unit of density is kg/m^3.