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A data transfer rate tells you how much digital data will travel from one place to another—from a hard drive to a USB flash drive, for example—in a specific period of time.
Rather confusingly, you’ll see it measured in:
The difference between bits and bytes is explained below.
However, with today’s technology being capable of transferring large amounts of data at fast speeds, you’re more likely to see it measured in megabits per second (Mbps) or megabytes per second (MBps). (A megabit is around a million bits. A megabyte is roughly a million bytes.)
Sometimes—when downloading a file from the internet, for instance—you might see the data transfer rate measured in kilobytes per second (KBps).
Most internet service providers use the Mbps figure when advertising the speed of their broadband/fibre products.
Bits | Bytes |
|---|---|
Used to measure speed (of a connection) Written with a lower-case b (e.g. 25 bps, 20 Mbps) Kilobit (kb)—1,024 bits Megabit (Mb)—1,024 kilobits Gigabit (Gb)—1,024 megabits Terabit (Tb)—1,024 gigabits | Used to measure size (of a data file) Written with a capital B (e.g. 30 MBps, 5 GBps) Kilobyte (KB)—1,024 bytes Megabyte (MB)—1,024 kilobytes Gigabyte (GB)—1,024 megabytes Terabyte (TB)—1,024 gigabytes |
A byte is the bigger unit—there are eight bits in every byte.
There’s a simple way to work this out, using the file size (bytes) and the transfer speed (bits).
It’s easier if you know the megabits per second figure in megabytes (MB). Remember, there are eight bits in every byte, so convert the transfer speed into megabytes per second (MBps) by dividing it by 8:
You now know that, at maximum, 12.5 MB of the file will transfer every second.
As the file is 250 MB in size, calculate its transfer rate by dividing 250 by 12.5:
It will take 20 seconds to transfer a 250 MB file across a 100 Mbps connection.
This is only a rough estimate, however, and there are several other factors that come into play.
There are lots of online tools that let you test data transfer rates. Most are called ‘internet speed tests’ or something similar, as they work by testing the speed of your internet connection.
People generally use these tools to make sure they are getting the broadband speeds their internet providers have promised them.
More sophisticated tools are available that can also test how efficiently your hardware is performing. These are typically software programs you download and then run.
The simple speed tests work by simulating a download and an upload of a data file and measuring the results. They assess the:
Some popular tools include the following:
Online speed tests
Speed and hardware testing software
Often, a slow data transfer rate is due to your computer’s hard drive. Fortunately there are ways to speed up your drive and get it performing more quickly, including:
These may sound complicated but implementing them is actually quite simple—you don’t need to be an IT expert! Just follow the step-by-step guides at MakeUseOf and Techwalla.
Another method is to upgrade from USB 2.0 to USB 3.0 (or higher)—the newest versions of USB are designed to transfer data at much quicker speeds.
Read more about USB data transfers here and about USB versions here.
It’s not always clear how to get the fastest data transfer rates. What version of USB do you need? What type of hardware? Are certain cables and connectors faster than others?
The tables below show data transfer rates for different:
USB version | Year | Speed | Transfer rate | |
|---|---|---|---|---|
Megabits/gigabits per second | Megabytes/gigabytes per second | |||
USB 1.0 | 1996 | Full speed | 12 Mbps | 1.5 MBps |
USB 1.1 | 1998 | Full speed | 12 Mbps | 1.5 MBps |
USB 2.0 | 2000 | High Speed | 480 Mbps | 60 MBps |
USB 3.0 | 2008 | SuperSpeed | 5 Gbps | 640 MBps |
USB 3.1 | 2013 | SuperSpeed+ | 10 Gbps | 1.2 GBps |
USB 3.2 | 2017 | SuperSpeed+ | 20 Gbps | 2.5 GBps |
Click here for an explanation of USB versions
Connector | Year | Transfer rate | |
|---|---|---|---|
Megabits/gigabits per second | Megabytes/gigabytes per second | ||
FireWire |
|
|
|
FireWire (IEEE 1394) 200 | 1995 | 196 Mbps | 24.5 MBps |
FireWire (IEEE 1394) 400 | 1995 | 393 Mbps | 49.1 MBps |
FireWire (IEEE 1394b) 800 | 2002 | 786 Mbps | 98.3 MBps |
FireWire (IEEE 1394b) 1600 | 2002 | 1.57 Gbps | 196 MBps |
FireWire (IEEE 1394b) 3200 | 2007 | 3.14 Gbps | 393 MBps |
Thunderbolt |
|
|
|
Thunderbolt | 2011 | 2 × 10 Gbps | 2 × 1.25 GBps |
Thunderbolt 2 | 2013 | 20 Gbps | 2.5 GBps |
Thunderbolt 3 | 2015 | 40 Gbps | 5 GBps |
eSATA |
|
|
|
eSATA (SATA 300) | 2004 | 3 Gbps | 375 MBps |
eSATA (SATA 600) | 2011 | 6 Gbps | 750 MBps |
Ethernet |
|
|
|
Ethernet | 1980 | 10 Mbps | 1.25 MBps |
Fast Ethernet | 1995 | 100 Mbps | 12.5 MBps |
Gigabit Ethernet | 1998 | 1 Gbps | 125 MBps |
10 Gigabit Ethernet | 2002–2006 | 10 Gbps | 1.25 GBps |
Media | File size | Speed of internet connection | |||||
|---|---|---|---|---|---|---|---|
|
| 4Mbps | 8Mbps | 16Mbps | 32Mbps | 50Mbps | 100Mbps |
One song | 5 MB | 10 secs | 5 secs | 2.5 secs | 1.25 secs | 0.8 secs | 0.4 secs |
YouTube video (SD) | 10 MB | 20 secs | 10 secs | 5 secs | 2.5 secs | 1.6 secs | 0.8 secs |
YouTube video (HD) | 50 MB | 1 min 40 secs | 50 secs | 25 secs | 12.5 secs | 8 secs | 4 secs |
Album | 100 MB | 3 mins 20 secs | 1 min 40 secs | 50 secs | 25 secs | 16 secs | 8 secs |
Episode of TV show (HD) | 450 MB | 15 mins | 7 mins 30 secs | 3 mins 45 secs | 1 min 52 secs | 1 min 12 secs | 36 secs |
Film (SD) | 700 MB | 23 mins 20 secs | 11 min 40 secs | 5 mins 50 secs | 2 mins 55 secs | 1 min 52 secs | 56 secs |
Film (HD) | 1.5 GB | 50 mins | 25 mins 30 secs | 12 mins 30 secs | 6 mins 15 secs | 4 mins | 2 mins |
Film (full DVD) | 4.5 GB | 2 hrs 30 mins | 1 hr 15 mins | 37 mins 30 secs | 18 mins 45 secs | 9 mins 22 secs | 4 mins 41 secs |
Film (full Blu-Ray) | 10 GB | 5 hrs 35 mins | 2 hrs 47 mins | 1 hrs 24 mins | 42 mins | 26 mins 40 secs | 13 mins 20 secs |
Because of how hard drives work—with rotating discs—and the way in which they store and access data, they are usually limited to a transfer rate of about 100 MBps–200 MBps.
The data transfer rate of a hard drive depends on the model and the interface it uses to function (usually SATA). However, it’s also a combination of two different types of transfer rate—the external transfer rate and the internal transfer rate.
The external transfer rate is usually faster than the internal rate because it’s purely electronic, and doesn’t rely on how efficiently actual physical components (the disk platters inside the drive) operate.
A Cat6 (Category 6) cable is the type of cable you’d use to transfer data over an Ethernet connection or network.
These cables are designed and made to transmit data reliably at high speeds and across a bigger range of frequencies. However, the data transfer rate does depend on the type of Ethernet connection.
For example, if you wanted to download a 4.5 GB DVD:
The Cat6 cable is the latest in a series of cables—Cat3, Cat4, Cat5—used for transmitting data via Ethernet. It’s the only Cat cable that supports the high speeds the 10 Gigabit Ethernet connection is capable of achieving.
This depends on which USB version the flash drive supports. The most recent versions of USB—3.0 and higher—deliver maximum transfer speeds of 5 Gbps (640 MBps) and above.
However, the specifications that the manufacturers of most of these USB drives provide warn that you’re unlikely to ever achieve the maximum possible speeds. With that in mind, you can expect transfer rates of 800 Mbps (100 MBps) or less, for USB 3.0.
This is generally because USB versions are developed for future technology rather than what we have at present, which isn’t capable of exploiting those versions’ full potential.
Comparing USB and Micro-SD is tricky in that you’re not really comparing like for like.
With USB 3.0, you get a read speed of 100 MBps, but much lower write speeds. With USB 3.1, you get read and write speeds of up to 400 MBps, and most new computers come with this capability.
Micro-SD memory cards, on the other hand, are each designated a speed class according to their minimum write speed. This write speed tells you what resolution of photo or video the device—a digital camera, video recorder or smartphone—is capable of recording (e.g. HD, 4K etc.).
The table below shows some of the different designations and speeds:
Speed class | Video formats | Minimum write speed (megabytes per second) | |
|---|---|---|---|
Speed Class | Class 2 | Standard Definition (SD) | 2 MBps |
Class 4 | SD High Definition (HD) (720p) Full HD (FHD) (1080p) | 4 MBps | |
Class 6 | SD HD FHD | 6 MBps | |
Class 10 | SD HD FHD 2K UHD 4K UHD | 10 MBps | |
UHS Speed Class | UHS Class 1 | SD HD FHD 2K UHD 4K UHD | 10 MBps |
UHS Class 3 | SD HD FHD 2K UHD 4K UHD | 30 MBps | |
Video Speed Class | V6 | SD HD FHD 2K UHD 4K UHD | 6 MBps |
V10 | SD HD FHD 2K UHD 4K UHD | 10 MBps | |
V30 | SD HD FHD 2K UHD 4K UHD 8K UHD | 30 MBps | |
V60 | SD HD FHD 2K UHD 4K UHD 8K UHD | 60 MBps | |
V90 | SD HD FHD 2K UHD 4K UHD 8K UHD | 90 MBps | |
Read more about SD speed classes at the SD Association’s website.
USB speeds are affected by how many devices are sharing one port. On many laptops, the USB ports are all routed through a single internal hub—if all the ports are being used, speeds will be slower.
A Micro-SD card in a digital camera or a smartphone is always going to be faster in the device than when it’s connected to a PC via a USB reader.
Again, this depends on the version of USB. The table above shows the maximum transfer rates for each version available up to now. The quality of the cable used will also be a factor.
Does USB 3.0 work with USB 2.0?—A guide to USB versions and compatibility
