An explanation of displayed speeds
In our broadband comparison tables, you'll find the same speeds that providers list on their websites.
But those adverts only tell part of the story.
The way providers express the speed of the connections they offer has changed over time, guided by changes in technology, and advertising and consumer regulations.
In this guide, we look at some other ways that ISPs can express the speed of the connections they offer.
We'll start by looking at how the speeds advertised have changed over time, then we'll look at how to get a more realistic idea of the speeds users can get in practice.
Advertised speeds over time
The table shows how the UK's biggest broadband providers have advertised the same products over the past five or so years, and Ofcom's independent research into the speeds users have actually achieved.
The biggest ISPs' advertised speeds, and Ofcom results, over time
|Pre-2012||Typical Speed Range (Ofcom 2012)||2012 to early 2014||Ofcom average (from 04/14 figures)||2014 on||Ofcom 24 hour average (Feb 2015)|
|BT||24Mb||3 - 9Mb||16Mb||8.8 - 11.1Mb||17Mb||8.9Mb to 11.8Mb|
|BT Infinity 1||40Mb||30 - 36Mb||38Mb||31.4 - 34.2Mb||38Mb||32.1Mb to 34.4Mb|
|BT Infinity 2||80Mb||70 - 76Mb||76Mb||61.6 - 68Mb||76Mb||59.9Mb to 63.1Mb|
|Sky||20Mb||3 - 9Mb||16Mb||8.8 - 10.6Mb||17Mb||8.6Mb to 10.6Mb|
|TalkTalk||20Mb||3 - 9Mb||14Mb||7.8 - 9.8Mb||17Mb||7.5Mb to 9.5Mb|
|Virgin Media: 30Mb||30Mb||-||30Mb||30.4 - 31.4Mb||50Mb||52.5Mb to 53.3Mb|
|Virgin Media: 60Mb||60Mb||57 - 59Mb||60Mb||59.2 - 60.4Mb||100Mb||94.3Mb to 99.5Mb|
|Virgin Media: 120Mb||120Mb||-||120Mb||113.2 - 116.7Mb||152Mb||129.5Mb to 135.8Mb|
Note the leap in the speeds of the Virgin Media packages in 2014. During the first half of the year they upgraded their network and the packages available; customers were automatically moved onto the newer, faster, version of their existing package.
What the figures mean
Until April 2012, the term "up to" was used to mean the theoretical maximum speed a connection could reach using the technology available.
There was no guarantee that users could actually reach those speeds - usually expressed as either 8Mb, 20Mb or 24Mb - and, in fact, some ISPs admitted that none of their customers would actually be able to achieve them.
Read more on the "up to" debate here.
From 2012 to 2014
In September 2011 the Committee of Advertising Practice (CAP) released new guidelines on how ISPs should advertise speeds, which came into effect in April 2012.
From that point on, the term "up to" has supposedly meant the speed that at least 10% of the provider's customers must be able to achieve on average.
In other words, it's still not a very helpful guide to the actual speeds we can expect from an ISP, but it's better than the old system.
For one thing, it's meant providers can adjust their advertised "up to" speeds as the performance of their network changes: in August 2013, for example, Sky's advertised speeds jumped from 14Mb up to 16Mb, based on their speed data.
But some broadband providers responded to the 2012 rule by removing speed information entirely.
For example, for a while we listed TalkTalk broadband as "up to 14Mb" at their request. But during that time trying to find out how fast their ADSL broadband using their own website was almost impossible.
At least when it came to fibre broadband they followed the BT model - as does every ISP that offers fibre over the Openreach network.
In the past year or so we seem to have returned to something approaching the bad old days of blanket speed claims - everyone now offers "up to 17Mb" ADSL broadband again.
It's partly because of the push to get Britain totally connected, the competition for custom in urban areas, and the slow improvement of services in less built up regions.
But there's also a marketing element to it: no one wants to be the one provider that offers less than 17Mb broadband.
Ofcom's take on broadband speeds
To get a better idea of the actual speeds achievable with each ISP, take a look at the figures released quarterly by the industry regulator, Ofcom.
Ofcom use 10 focus groups from around the UK to get a rounded picture of what those advertised speeds translate into in practice.
Groups vary by location, and rural areas are counted as well as cities like London, Manchester, Cardiff and Edinburgh. Within each group users are at different distances from the exchange, and use the internet in different ways.
Ofcom then publish the maximum speeds achieved, and the average speed over the course of a day, and at peak time (between 8pm and 10pm).
When we updated this article we used the most recent results, from February 2015, which you can access here.
Typical speed ranges
During the CAP guideline consultation, Ofcom suggested that ISPs display a Typical Speed Range (TSR) to more accurately represent the range of speeds consumers can expect.
Using the same data that they collected for the averages above, the regulator suggested that providers display two halves of an inter-quartile range - the average speeds achieved by the 25th and the 75th percentile.
The result is a pair of numbers that reflect the range of speeds achieved by exactly half of an ISP's customers.
But there didn't seem to be much enthusiasm for the idea, and Ofcom themselves stopped releasing ranges in 2012. We've included the last batch in the table above to show how they worked.
Minimum Guaranteed Access Line Speed
In 2015, however, Ofcom have come back to the idea of an acceptable range of speeds.
Under the terms of a strengthened Code of Practice, which will come into effect in October 2015, the ISPs must provide potential customers with information about the range of speeds achieved by similar households.
This time around, the range will be based on the speeds achieved by the middle 60% of similar households; the slowest 20% and the fastest 20% of connections can be ignored.
On top of that, customers will have the right to leave their ISP at any time during their contract if their connection drops below a certain speed.
Here's the sting: that minimum access speed is equivalent to the fastest of the slowest 10% of connections using the same service.
Say we're looking at ISP with 100 customers in our area.
When we're thinking of signing up, the ISP will tell us we can expect a connection ranging between that experienced by the 20th fastest and the 80th fastest - but we won't be able to leave unless our own connection drops below that of the 90th fastest.
The best speed average for individuals
While ranges and averages are all well and good, they don't help us pin down likely speeds for those of us not in the areas covered by Ofcom's focus groups.
What they do offer is a comparison between the different providers.
Virgin Media's fibre optic cable network gives customers connections closer to the maximum speeds offered than their equivalents on the BT Infinity FTTC network, for example.
We can also get an idea of the variety of speeds we're likely to see. Do connections seem to suffer particularly at peak times, or are they consistent across the day?
Ofcom also tend to report on factors like contention and upload speeds, which can be just as important in receiving a smooth service as how fast the connection is.
However, in terms of the actual speeds an individual household will be able to get, it's still somewhat lacking.
As we look at here, there are other factors that can affect the speed of your connection, from the number of people on your network, to the wiring in the building.
Anyone suffering from a slow connection should have a look at our guide to improving it without changing provider, here.
Those determined to find the best available speed really have only one option: click through to an ISP's website and get an estimate from them.
An estimate, of course, is just that - and were it to become the guarantee upon which our contract relies, the providers would have plenty of incentive to aim low.
Would that be enough to prompt realistic advertised speeds?