Internet Speeds Explained

Internet-speed-test-150x150Judging by the amount of searches done for the term “speed test” there seems to be a bit of an obsession with Internet speeds and what is a good upload and download speed.

There are many online test tools that allow you to check your upload and download speeds.

In this tutorial I will try to explain upload and download speeds,   how internet speed tests work and what they are really telling you. We look at.:

  • What is a good download speed and upload speed?
  • What does Mbps mean?
  • Is a download speed of 10 Mbps good?
  • Do Internet speeds vary throughout the day.
  • Is it worth changing providers to get a faster internet connection?

Understanding Internet Speed Tests

Internet speed tests will give you an upload speed and download speed.

Uploading refers to the process of transferring data from your computer to the Internet, and downloading refers to transferring data from the Internet to your computer.

Usually the download speed is much greater than the upload speed (ADSL and VDSL).

This is usually OK because for most people they download much more than they upload.

Download speed tests work by transferring a file of a known size from a test server located on the Internet to your computer, and measuring how long it takes.

A 4 MB file will take 8 secs over a 4 Mbits/s link and 2 seconds over a 16 Mbits/s link. (see Bits and Bytes).

The upload speed is measured by uploading a file from your PC to the test server on the Internet and again measuring the time taken.

There are many online speed test tools you might want to try such as :


There are several factors that affect how fast your overall connection speed is:

  • The access technology- e.g. ADSL,4G/3G mobile, Satellite etc
  • Your ISP.
  • The location of your destination server or service.

They all combine together to form a chain (communications link) . As a comparison, If you imagine traffic driving down a 6 lane road, which becomes a 2 lane road and.then a 4 lane road. (image Below).


You can see that the traffic will be restricted by the 2 lane road.

On the Internet, just like on a normal road, your final speed will be limited by the slowest link in the chain.

Note: You do not need to install any software on your computer to do a Internet speed test. Be very wary when using speed test sites as some with prompt you to install software to improve your computer speed. Some probably are genuine, but it is impossible to tell, so I wouldn’t do it.

Internet Speed Factors

Several factors affect your internet access speeds:

  • Your Internet Access technology
  • Your ISP
  • Location of the remote resource
  • Time of Day

Internet Access Technology

This is the most important factor as far as internet access speed is concerned.

All technologies have limitations. The connection speeds of fibre broadband is far superior to 3G mobile.

See common Internet access methods. for an overview with pros and cons of each technology

Your (Internet Service Provider) ISP

You connect to your ISP (using an access method e.g. ADSL Broadband) and your ISP then connects to the Internet.


ISPs advertise the connection speeds to the subscriber, and not the speeds between the subscriber and the Internet.

In the UK the connection to the home is almost always a BT phone line and ADSL, but fibre is becoming increasing popular.

If that is the case then The access speed will be limited by these BT lines regardless of the ISP you choose.

However that doesn’t mean that all providers will provide the same overall connection quality as-.

The connection between the ISP and the Internet is usually over fibre and is fast, but it is shared by many subscribers.

Therefore if the ISP overloads the link to the Internet it slows the connection from subscriber to Internet.

So your Connection to the ISP could be 6Mbits/s but from you to the Internet it could be only 3 Mbits/s.

Here is a quote from the BBC article on broadband speeds

Almost half of broadband users are now on packages with advertised speeds above 10Mbps but the average broadband speed is 6.8Mbps according to Ofcom.

The Location Of The Service/Server On The Internet

The Internet comprises a vast network on interconnected computers and networking equipment e.g routers (diagram below).


The number of routers/servers that the data must travel through on the way to and from the destination service/server will affect the overall speed.

In addition the speed and capacity of the network that inter-links these computers/routers will also affect the final connection speed.

In general the Internet itself will often be the limiting factor that affects your overall internet speed.

So you may have a super fast connection to the Internet, but still take the same amount of time to download a file from the Internet as someone with a much slower Internet connection.

Time of Day

You may have noticed that the Internet appears to slow at certain times of day.

This is very similar to rush hour on the roads.

Here is a uswitch graph showing Internet speeds in the UK over the day.


Notice how the average speed drops from almost 10Mbps to around 6Mbps.

The worst time to be surfing the net is between 7pm and 9pm.

When doing speed tests it is a good idea to do several over the course or a normal day.

Download vs Upload Speeds

When you view a website with a web browser you are downloading information from the Internet.

Most people spend most of the time surfing the Internet, and downloading information, which is why the download speed is usually more important than the upload speed.

It is the speed that broadband providers usually display, and what people compare.

Here is a screen shot of the standard BT broadband package, and notice there is no mention of the upload speed.


If you send email then that email is uploaded from your PC to the Internet.

If you post pictures or videos on YouTube or Facebook then those pictures/images are uploaded to the Internet.

How long that takes will depend on the upload speed of your connection.

Most broadband packages provide broadband over telephone lines, and use a technology called ADSL (Asynchronous Digital Subscriber Line ) which has a much faster download speed than upload speed.

If you have an existing broadband connection you can check your upload and download speeds using an online speed tester. Here are my results:


Notice that the upload speed is 21 times slower than the download speed. This means that a file that could be downloaded from the internet in 30 minutes would take over 10 hours to upload to the Internet.

Most Internet users aren’t currently interested in uploading files to the Internet, but with the growth in popularity of online storage there could be a increase in demand for much faster upload speeds.

The newer fiber packages from the main UK broadband providers (BT, SKY, Virgin,Talk Talk) offer significantly faster upload speeds as well as faster download speeds

The screen shot below shows the BT Infinity package with a download speed (76Mb) , which 4 times faster than the upload speed (19Mb).


If you are considering using the Internet for transferring large files then you should look for a broadband package that offers fast upload speeds.

What is a Good Upload or Download Speed?

This really depends on what you want to do with the Internet connection and also what access technology you are using.

A good upload speed on ADSL would be much lower than a good upload speed on fibre.

If you want to download and stream movies then a minimum of 4Mbps is needed.

If there are several people in your household that also watch movies online then you would want a little more speed.

The best indicator of slow network speeds is obtained by using the Internet.

If you find that that web pages take a long time to load, and movies take a long time to buffer, then you should check your speed.

An easier check is to check your ISP advertised speeds against your own speed.

You might find that you are paying a premium for a package because of the advertised speed, but it is impossible for you to get those speeds because of your location.

Internet Speed Checkers

They are many websites that allow you to check your Internet speed like this online speed tester.

However if you want to monitor your Internet speed on a regular basis then I recommend the command line tool called speedtest-cli.

This Github page as the install and usage instructions

If you are interested in monitoring your speed on a regular basis take a look at my node-red speed test flow


Internet Speed tests are useful for checking that you aren’t paying for a connection that you aren’t getting.

However your connection speed is only one part of the overall Internet connection, and you are unlikely to notice the difference between a 10Mbit/s connection and a 6Mbit/s connection when watching, for example, a YouTube video.

The more people you have accessing the Internet through your connection the more important your connection speed becomes.

Bits and Bytes Explained

A byte has 8 bits. The size of files stored on your computer is measured in bytes.

1KB =1 kilo Bytes =1,000 Bytes and 1MB=1 Million Bytes.

When measuring data transmission speeds the measurement is bits per second or bps


1 kbps =1 thousand bits per second and 1Mbps= 1Million bits/sec

Notice bits has small b and bytes a large B.

Internet Speed Monitor

If you would like to monitor your Internet updload and download speed on a continuous basis then take a look at  my internet connection monitor tool. Monitor Internet Speeds with Speedtest-cli and Node-Red


Common Questions and Answers

Q- I measured by upload and download speeds and they are very different to what the broadband provider advertised. Is this normal?

A- Yes. ISPs usually quote the best speeds possible in theory, but not in practice.

Q- I measured by download speed and it is XMbps is it fast enough?

A- It depends on what you do, or want to do with the connection and how many people use the connection. Generally speeds above 6-8 Mbps will be good for most applications.

Q- My Internet connection is slow what is the reason?

A- It is difficult to say for sure. It could be your connection to your ISP or it could be the Internet. If you check your connection and find that your download speed is around 6Mbps or faster then it is likely to be the Internet.

Q- Is it worth changing providers to get a faster internet connection?

A- Because of the way broadband is provided it is usually better to try changing the access method i.e. go to fibre instead of ADSL.

Q- Can my Wi-Fi be responsible for my low speeds?

A- Yes if you are using old Wi-Fi adapters in your laptop/PC. For example the old 802.11a standard peaked at around 5Mbps. See this Yahoo answer and this about google support tip for details

Q- I am using Cloud storage for backing up data what should I check?

A- You need to check your upload speed. Generally only fibre broadband supplies good upload speeds.

Q- Is 6 Mbps fast?

A- You can judge it’s speed by how long it takes to transfer data. A 6 MB file will take 8 secs over a 6 Mbits/s. A standard 1GB movie will take about 22 minutes to download at 6Mbps.

Q- What is more important upload speed or download speed?

A- For most people it will be the download speed as most people will be browsing the web downloading movies etc.

Q- Is it possible to monitor Internet Traffic?

A- To do this the Home router must support this and unfortunately most ISP provided routers don’t.

My BT provided home router provides a summary of upload and down traffic but there is no way of know what type of traffic or which devices are responsible for the traffic.


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  1. Thanks Steve, for the easy to follow information on internet speed! I’m in Michigan (USA) and my download speed hovers around 300 mbps with an upload speed of 25 mbps. Our ISP is Xfinity. I feel pretty fortunate to have access to those speeds; I’m an information junkie and research pretty much everything that comes to mind during the day (I’m retired, so I can do that : ). Again, thank you.

  2. Hello. I am with Sky fibre (the fastest package they offer) and I’m getting 68mb to the router. When I plug in an Ethernet cable into my pc, it downloads at between 5.5mb and 7mb per second depending on the time of day. This seems very low download speeds considering I’m using a wired connection to a 68mb router. I’ve tried everything to solve the issue apart from cancelling my package with sky. Is there anything you can suggest or should I be expecting to only have real download speeds of 5.5-7mb? Thanks.

    1. Are you going through an old switch or is your PC using an old network card? I assume it is a wireless router what are you getting with your phone?

  3. Dear Steve, “You might find that you are paying a premium for a package because of the advertised speed but it is impossible for you to get those speeds because of your location.”
    With the, finally!, big push to get fibre optic networks into every (UK/Europe) home these days, I am having trouble finding a reasonably comprehensive, cascading-chart understanding of how best to set up a fairly future-proofed home network capable of serving, let’s say, 10 or a dozen 4K monitor screens with HDTV, potentially concurrently!, for the next generation of grandchildren as it were.
    So, without going into the possibilities into the future with upcoming 5G mobile networks for portble devices, the following interlinking aspects concerning the use of fibre optic cable landlines seem to arise:-
    1. how best to select an incoming fibre optic package speed;
    2. How is the incoming fibre optic internet datastream best connected into the home –
    a. by an internal onward fibre optic network of some cost-effective kind,
    b. by some grade of ethernet cable – Cat 5e/6? – or,
    c. by a high speed wifi network
    3. I believe that my existing ADSL router is also capable of receiving a fibre optic incoming connection, so is standard wifi 802.11n speed enough to serve such a maximum demand as set out above.
    Clearly there will be cost pinch points where it just becomes unjustifiable to install high-grade equipment largely for the sake of it, and so some overall advice, quoting the relative speed interfaces along the way, would be very helpful, bith for myself and I’m sure for others who may well be similarly interested to see such an overall picture in one single place.

    1. John
      Difficult to say as there are so many variables.
      The fibre optic depends really on your location. In my location which is rural I can’t get it. Needless to say if you can I would go for the starter option as you can always upgrade the package if the speed isn’t up to it.
      In the home I would go for wired connections were possible (cat 6 or 5e). If that is not possible I would for homeplug and wireless for those devices that don’t have Ethernet.However if the devices support wi-Fi 6 then use that if they aren’t too far away.
      Have you seen this tutorial
      Although wired connections are faster and more stable I would personally only go for creating new wiring if I was doing major renovations or new build.
      Hope that helps.

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