What is Megabytes & gigabytes?

In plain English

Megabytes (MB) and gigabytes (GB) are simply units for measuring the size of digital things — files, photos, apps — and how much room you have to store them. Think of them like litres of water: a litre is small, a thousand litres fills a paddling pool. A megabyte is the small unit; a gigabyte is about a thousand megabytes — the bigger jug.

So a single email might be a few MB, a holiday photo around 3–5 MB, and a long video several GB. When your Windows laptop or Android phone says it has "256 GB" of storage, that's the size of the cupboard you're filling up. The more MB and GB something takes, the more space it eats and the longer it takes to download.

Why it matters

These numbers crop up everywhere, and getting them muddled costs money or causes headaches. Buy a phone with too few GB of storage and it'll be full of photos within a year. Misjudge your broadband and a film that's several GB can chew through a capped data allowance — or take an age to arrive. For a small business, knowing your file sizes helps you choose the right amount of cloud storage and backup space, so you're not paying for a warehouse when you need a shed, or vice versa. A little understanding here saves you from overspending and from that dreaded "storage full" message at the worst moment.

What to do

• Check before you buy: on a Windows PC, go to Settings > System > Storage; on Android, Settings > Storage. It shows GB used and free, so you'll know if you're running low.
• Rough rule of thumb: 1 GB holds roughly 250 photos, or a few hundred songs, or about 30 minutes of video — handy when sizing up a new device.
• Watch your data allowance: if your broadband or mobile plan is capped, large GB downloads (films, big updates) are what use it up fastest. Do those on home Wi-Fi where you can.
• Free up room rather than panic: photos and videos are usually the culprits. Moving them to the cloud or an external drive is far cheaper than a new device — and don't worry, this is a five-minute job we sort for people all the time.

How 365 Techies can help

If you're not sure whether you're running out of space — or how many GB you actually need on a new computer or phone — we're happy to take a quick, jargon-free look and point you in the right direction.

Related: Hard drive · SSD · The cloud · RAM — or browse the full A–Z jargon buster.