What’s the difference between bytes, megabytes and gigabytes?

By now, you might have seen a television advert promoting the latest in a long line of retro computers – The Spectrum.

As we recently discussed, retro computer gaming has become a phenomenon over recent years.

However, younger gamers might be shocked by the crude graphics associated with Spectrum games – literally and metaphorically basic in construction, often monochrome and generally jerky.

This 1980s home computer lacked the graphics processor units of modern devices, but it also lacked the random access memory needed to multitask and run quickly.

Most versions of the Spectrum had just 48 kilobytes of memory. Early versions debuted with 16, while the less iconic +2 sequel upgraded to 128K.

But what does a kilobyte comprise, and how does it scale up into megabytes, gigabytes and terabytes?

Understanding this concept will make it easier to choose your next computer or smartphone, cloud-hosted storage solution or physical hard drive/SD card/USB data key…

Okay, I’ll byte

Bytes, megabytes and gigabytes are multiples of the same unit of digital storage – a byte, which contains eight binary bits of data.

As we explained in this article, a bit is the binary state every electronic device uses to understand instructions. On or off, zero or one.

Clearly, it takes a vast number of zeroes and ones to power Call of Duty, or the Sky EPG, or Android Auto. Yet binary is the only language computers truly understand.

As such, one bit – a single on/off decision – doesn’t offer much scope for instruction or sophistication.

Bundle eight bits together into a byte, and you’re starting to make some progress. A thousand bytes make up a megabyte, which is a sufficiently large data volume to be genuinely useful.

In the 1990s, 3.5-inch floppy discs (which weren’t actually floppy, unlike their 5.25-inch ancestors) stored 1.44 megabytes of data.

A compact disc typically hosted 700MB of data, while a single-layer DVD could host 4.7 gigabytes.

A gigabyte is a thousand megabytes, just as a megabyte is a thousand bytes.

Perhaps inevitably, a terabyte – a unit increasingly associated with computer hard drives and even some high-end smartphones – is a thousand gigabytes.

Plenty in store

Having established the numerical sequencing of bytes, megabytes and gigabytes, it becomes important to consider how these volumes are used.

A DVD may be theoretically capable of hosting 4.7GB of data, but a typical 90-minute film might only occupy half that space even in 4K format, thanks to compression codecs.

Similarly, your smartphone might come out of its wrapper promising 512MB of storage (512 megabytes equals half a gigabyte), but much of this space will already be in use.

Operating systems, bloatware, essential apps and services tend to consume a portion of the total available storage – an argument for always buying more storage than you need.

Games, self-generated photos and videos, apps and downloaded media (like music) could also consume many gigabytes of storage over time.

Capacities are therefore less important than your plans to utilise them. A 128GB tablet will be sufficient if all your document and files are saved to the cloud, rather than locally onto the device.

However, you’ll need to understand the scale of bytes, megabytes and gigabytes to accurately make these assessments.

It’ll also put into context how miraculous the Spectrum and other 8-bit computers were in achieving so much with so little memory…