Background information

Why your USB stick gets lighter when it’s full

21.6.2025

Translation: Katherine Martin

This may seem like a daft question, but does storing data on a USB stick make it heavier? As it turns out, the answer’s even more mind-boggling than the question.

I’ve been a self-confessed e-reader fiend for some time now. I mean, come on. A display that looks like paper but lights up at night? Seemingly never-ending battery life? What’s not to love? Not to mention the fact that e-readers are lightweight. In fact, my Tolino Shine tips the scales at just 173 grammes. It’s a godsend compared to hefty books, which sometimes weigh up to a kilo.

Product test
Small, robust, good: the fifth Tolino Shine almost passes my test with flying colours
by Martin Jungfer

Plus, my e-reader has storage space for up to 12,000 titles, so I don’t have to lug around a load of extra weight…Or do I? Does data weigh anything? Do USB sticks or SSDs get heavier when files are stored on them?

You’d intuitively assume that a full USB stick would be heavier than an empty one, as there’d be «more» on it. Paradoxically, however, the opposite is true. The more data you have on your USB, the lighter it’ll become. But how?

Memory in a nutshell

To understand how USB sticks get lighter, we need to look at how storage devices actually work.

These days, virtually all data storage devices – USB sticks, SD cards and SSDs – are based on the same principle: NAND flash memory. Unlike HDDs, records or magnetic tape, flash memory involves files being stored purely electronically and in binary form on transistors, the famous 1s and 0s.

Each bit – i.e. each transistor – on a storage medium can be either empty (0) or full (1). So far, so good. Electrons are charged or discharged on these transistors to change their state, i.e. to add or remove data. This is where things get interesting. Contrary to what we might expect, a charged transistor corresponds to a 0, while a discharged transistor corresponds to a 1. Again,: charged transistor = 0 = no data; discharged transistor = 1 = data.

Think of the old punch cards from the early days of computers. An empty card had no holes, so there was more material there. In order to write data to the card, holes were made, removing material at the same time. Modern-day flash memory, however, is all about energy, not material. A full transistor doesn’t allow any more electricity in, and is interpreted as 0.

Of course, this is a very simplified explanation of things. In reality, the issue is much more complicated. But it’s fine for our thought experiment.

What does your USB stick weigh?

With all of this in mind, we’re ready to calculate the weight difference between an empty USB stick and a full one (spoiler alert: it’s not much).

A single electron has a mass of 9.11e-31 kg or exactly 0.0000000000000000000000000000911 grammes. On a 64 GB USB stick, there are about 512 billion bits, each of which can potentially hold an electron. If we extrapolate that, a full USB stick of the same capacity would be a whopping 0.000000000000000466 grammes lighter than an empty one. Like I said, this is all very simplified.

Even so, you can still see that the weight difference is practically zero in real terms. To measure a difference of just one nanogramme, you’d need over a trillion USBs. For comparison, a dust particle weighs around 100,000 nanogrammes. Realistically, your USB stick will lose more weight as a result of the physical wear and tear on the contacts caused by plugging it in or removing it from a device than by transferring data.

Loaded with a whole lot of…nothing?

Let’s circle back to my e-reader. With 64 GB of storage space, it has room for an impressive 12,000 virtual books (I currently have eight in my collection, by the way). And yes, in theory, my e-reader would be slightly lighter if I actually had 12,000 books stored on it. Even if that seems totally counterintuitive.

If we’re being real for a second, this weight difference is unlikely to impact whether my hand luggage would be considered too heavy to take on a flight. Instead, I’d be better off rethinking my decision to take three pairs of swimming trunks, when I could probably get away with two.

Header image: Dayan Pfammatter

136 people like this article

Dayan Pfammatter

Freelance Editor

pf.dayan@gmail.com

I've been fascinated by all things keys, displays and speakers for basically as long as I can remember. As a journalist specialising in technology and society, I strive to create order in the jungle of tech jargon and confusing spec sheets.

Background information

Interesting facts about products, behind-the-scenes looks at manufacturers and deep-dives on interesting people.

Show all

These articles might also interest you

Background information
Why the world’s largest e-car never needs to charge
by Dayan Pfammatter
Background information
My own NAS system: my Unraid setup for the best overview and performance
by Richie Müller
Background information
What’s in my bag: Philipp’s all about that hemp
by Philipp Rüegg