Bits and bytes explained

Can't tell your bits from your bytes? Read on to learn the difference and figure out what broadband speed you need.

Connection speeds and data sizes are measured differently, but people tend refer to them both as 'megs'. The problem is that the word 'meg' actually refers to two very different values: megabits and megabytes. Aren't they the same thing?

Actually no, there's a big difference between a bit and a byte. A byte is much bigger — eight times bigger, to be exact, with eight bits in every byte. By extension, there are eight megabits in every megabyte, and one gigabyte is eight times bigger than one gigabit.

Bits, bytes and broadband speeds

You may be wondering how this relates to you and your broadband speed.

Data sizes are usually measured in 'bytes', and broadband speeds are measured in 'bits'. Based on the file size and your connection speed, you can estimate how long it'll take you to download something.

Let's say you find a file online that is 17 megabytes (MB) in size, and you want to download it using your 17 megabit per second (Mbps) broadband connection. This won't take one second; it will take eight times one second because a megabyte is eight times bigger than a megabit. So in theory — and with a perfect speed — it should take eight seconds to download.

Before you start reaching for your calculator, read our guide to download times. We've pulled together a list of the most common broadband speeds and file sizes to give you an idea of how long it will take to download films, TV series, songs and more.

How can I tell the difference between a bit and a byte?

From how it's written. A byte is an uppercase 'B' and a bit is a lowercase 'b'. If it says MB, all capitals, then it is a megabyte. If it says Mb, then it is a megabit. There is one exception to this, of course, and it is the symbol for kilobit, which is 'kb', all lowercase.

It's easy to figure out based on common sense: an uppercase 'B' is physically larger than a lowercase 'b', and a byte is larger than a bit.

Other file sizes to know about

While there are many different file sizes, most of us only need to know a little bit (no pun intended) of prefixes. Here are the most common ones.

• KB, MB, GB - A kilobyte (KB) is 1,024 bytes. A megabyte (MB) is 1,024 kilobytes. A gigabyte (GB) is 1,024 megabytes. A terabyte (TB) is 1,024 gigabytes.

• kb, Mb, Gb - A kilobit (kb) is 1,024 bits. A megabit (Mb) is 1,024 kilobits. A gigabit (Gb) is 1,024 megabits. A terabit (Tb) is 1,024 gigabits.

Don't forget! There are eight bits in a byte, so to translate from one to the other, you can multiply or divide by eight. For example, if you want to transfer 38MB across a 38 Mbps connection, it will take eight seconds.

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