What do quoted broadband speeds actually mean?

Monday, 26 November, 2018

When you consider computers and the internet are powered entirely by the binary programming system of zeroes and ones, the systems of measurement seem unduly complex.

Few people could confidently explain the difference between bits and bytes, let alone why download speeds outstrip upload speeds across domestic broadband networks.

Fortunately, we’re here to demystify the often baffling world of quoted broadband speeds…

Getting the bit between your teeth

Everything we do on a digital device involves binary data – tiny fragments of information coded as zeroes and ones, which collectively provide instructions about what should happen.

Binary data is typically measured using two related units – bits and bytes.

The multiplication table for these units is base eight, and there are eight bits in a byte.

Rather than using the metric system (where a kilo equals 1,000), base eight produces multiples which are slightly larger than you might expect.

A kilobyte is 1,024 bytes, and a megabyte is 1,024 kilobytes. This continues through gigabytes, terabytes and so forth.

Know the difference

Confusingly, bits and bytes are both used to measure data volumes.

When we’re talking about file sizes, we tend to refer to megabytes and gigabytes – the uppercase MB and GB respectively.

A typical MP3 file will be around 4MB in size, and so will a high-resolution JPG photo.

If your smartphone has a 64GB storage capacity, it can store 64 gigabytes of information.

However, data transfer speeds are measured using the smaller unit of bits – one-eighth of a byte.

They’re measured per second, and represented as Mbps, Gbps and so forth.

This is the figure you’ll see on Broadband Deals, explaining how fast an average internet connection will be over a typical second.

A typical broadband connection into your home might distribute data at 16Mbps – 16 megabits per second, or the equivalent of two megabytes per second.

Theoretically, a 4MB photograph would download over a 16 Mbps connection in two seconds.

In reality, quoted broadband speeds need to be taken with a pinch of salt.

Why do speeds vary?

Numerous factors affect the performance of a line at any given time – the number of people using that connection, the total volume of internet traffic being distributed worldwide, etc.

Industry regulator Ofcom has tightened the rules on advertised speeds, so any quoted average speed must be available to 50 per cent of customers between 8pm and 10pm.

However, internet connectivity constantly fluctuates, while average speeds are calculated over broad geographic regions – and occasionally across the entire UK network.

Why are uploads so much slower?

Most of the data we consume is delivered to us, but our devices are constantly sending requests for information and uploading data themselves.

Think about sending emails, posting Instagram selfies or playing online games where a central server requires real-time information about your movements and selections.

Rather than ensuring uploads and downloads each receive 50 per cent of available bandwidth, broadband providers prioritise downloads as being more important.

That means upload speeds can be as little as five per cent of download speeds.

This is fine if you mainly use the internet for streaming, but it’s an annoyance if you regularly send large documents via WeTransfer or participate in video calling.

There’s not much you can do to improve upload speeds, so it’s worth investigating this figure when researching a prospective new broadband provider.

Quoted broadband speeds don’t include upload data by default, but averages are usually available with a little research.

Neil Cumins author picture


Neil is our resident tech expert. He's written guides on loads of broadband head-scratchers and is determined to solve all your technology problems!