Weight and mass: not the same thing!

Uploaded on October 31, 2025

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Weight and mass: not the same thing!

Did you know that in everyday language we often use the word “weight,” but what we're really talking about is mass? Canadian Space Agency Data Scientist Roksana Sheikholmolouki explains these science concepts commonly misunderstood by students. 

We would like to thank, for their collaboration and expertise: 

Julie Bolduc-Duval, Discover the Universe

Gabrielle B. Durand, École en réseau

Charline Liard-Arbour, Centre de services scolaire des Samares (Credit: Canadian Space Agency)

Did you know that the weight of an object is measured in newtons, and not in grams or kilograms?

Ok. Hear me out!

It’s a common mistake. In everyday language, we often use the word “weight,” but what we’re really talking about is mass.

Mass is usually measured in grams or kilograms.

Simply put, mass corresponds to the quantity of material in an object, whereas weight is the force that gravity exerts on that object.

Here, I’ll give you an example!

Take an astronaut on Earth.

Let’s say that they have a mass of 115 kg, when they’re wearing their bulky spacesuit.

If they try to jump, it will be very hard to do because of their weight.

So now, let’s say that the astronaut is on the Moon.

The Moon pulls them with six times less strength than on Earth because its gravitational field is six times weaker.

So the astronaut’s weight is six times less.

But their mass – their quantity of matter – is still the same.

What would happen if they tried to jump on the Moon?

Because their weight is less, they can jump higher!

To conclude, mass and weight are closely related concepts. It’s not big deal if you mix them up in everyday life. But in science, it’s important to use the right word for the right concept!

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