So after my last article, I got asked a few questions about data and speed. Speed is one I’d like to write about but I think it’s a bigger topic than I have time for at the moment but I figured a little info on data should be easier (easier, not necessarily easy) to tackle.
Bits
In the digital world, everything breaks down to binary. Binary is just “base 2”, or 0’s and 1’s.
When it comes to measuring data, a binary 0 or 1 is a “bit” (short for binary digit). So think of bits as the building blocks of what we’re talking about.
You probably see more about bits than you think. Speeds for data transfer (how fast your download is going, or how fast your connection plan is) are typically represented in bits. But just like we deal with grams and kilograms to represent varying scales of weight (where a kilogram is just an easy term for 1000 grams) we do the same for bits.
Now there’s two ways that this can be done. In dealing with weight, we do things in tens, hundreds, thousands etc. (decimal) and we can do that for bit’s too.
| Common term | Unit | Bits |
| Bits | bit | 1 |
| Kilobits | Kbit | 1000 |
| Megabit | Mbit | 10002 |
| Gigabit | Gbit | 10003 |
| Terabit | Tbit | 10004 |
So the same way kilo is a prefix for kilogram to represent 1000 grams, we use the kilo prefix to bit’s to represent 1000 bits. There’s another prefix for each increasing power of 1000. In the above table you see mega, giga and tera; it keeps going too with the next few being peta, exa, zetta and yotta tops out as 10008 or 1,000,000,000,000,000,000,000,000 bits, or 1000 zettabits! Confused yet?
Well if you haven’t fallen asleep yet, let’s now look at the binary power version. This is the more pure version in my opinion but some people find the maths of 10’s easier.
| Common term | Unit | Bits |
| Bits | bit | 1 |
| Kibibits | Kibit | 1024 |
| Mebibit | Mibit | 10242 |
| Gibibit | Gibit | 10243 |
| Tebibit | Tibit | 10244 |
These go higher too but you get the idea. The really confusing part is that the terms for the decimal versions used to be commonly used (and sometimes still are) when the decimal version is actually meant (even I usually mean 10243 when I say Gigabit) so it’s often hard to know which is really intended. The units can also often be shortened too, so you’ll see Mb instead of Mbit (or Mibit), and the main thing to note is the lower case “b” which points to bit’s.
If you’re on a lovely 100/50 “UltraFast Broadband” fibre connection, the 100/50 really means you have a rated download speed of 100Mbit’s per second down, and 50Mbit’s per second up. A point that illustrates also that speed measurements represented by bits are also given against a unit of time (usually seconds). The speed you practically see on your connection varies significantly and certainly don’t expect to see every download or speedtest you see to show 100Mbit/s – as I said above there’s a bunch of info for another topic.
Bytes
A byte is a collection of 8 bit’s. Simple as that. The way those 8 bits are arranged defines what the byte represents. There are lots of different standards as to how that byte is interpreted but that’s another topic all together.
We do the grouping stuff here too, so we get Kilobyte, Megabyte, Gigabyte etc. We get the abbreviated units too, so KB, MB, GB (note the uppercase “B” here points to Byte’s instead of Bit’s). Technically the binary versions here get the abbreviations KiB, MiB, GiB etc., but again the terms get mixed up regardless of intention.
Bytes are usually not used to represent speed, but more commonly storage. So your harddrive in your computer will usually be measured in GB or more commonly now TB. For example I have several 2TB drives in my computer. If your internet connection has a data cap it too will usually be represented in byte’s instead of bits.
Some math
If you’re still with me, let’s do a little exercise to put what we’ve learnt to use.
Let’s work out if your downloads actually go at 20Mibit/s, how long will it take you to download a 4GiB file (for clarity, I’m going to use the binary version of both here).
First I’ll do some work on the speed to get it to a more useable number.
Times 20 by 60 to go from Mibit/s to Mibit/minute. 20 * 60 = 1200Mbit/minute.
Now, since there’s 8 bit’s in a byte and we measure our file in byte’s we can divide the Mibit’s/minute by 8 to get MiB/minute. 1200 / 8 = 150MiB/minute.
Now let’s get the file size from Gigabytes to Megabytes.
1 GiB = 1024 MiB so we times our 4GiB by 1024. 4 * 1024 = 4096MiB.
So, now we have a 4096MiB file, and we can download at 150MiB per minute.
4096 / 150 = 27.3 (minutes).
So all things going well (which they rarely do) you could download your file in a little under half an hour.
Another application of this sort of maths is working out how much data you will use while streaming video or music from the internet. I won’t put as much explanation around this one, but we’ll work out how much data I’ll use if I steam an hours’ worth of Netflix at high-definition which Netflix rate as about 5Mibit/s.
1 hour * 5Mibit/s = ???
60 minutes * 5Mibit/s = ???
60 minutes * (5 * 60)Mibit/minute = ???
60 minutes * 300Mibit/minute = ???
60 minutes * 300Mibit/minute = 18000Mibit’s
60 minutes * 300Mibit/minute = (18000 / 8)MiB’s
60 minutes * 300Mibit/minute = 2250MiB’s
60 minutes * 300Mibit/minute = (2250 / 1024)GiB’s
60 minutes * 300Mibit/minute = 2.2GiB’s
So for every hour you watched you’d use over 2 gigs of data. If your plan has a 100GB (or GiB depending on what they mean) quota that’s not too bad. If you have a 3GB quota… you’re going to run out of data pretty quick.
More reading? Wikipedia as usual has a tonne (another of those units of measurement) of information. You can start with their article on the Bit and go from there.
That’s enough for now. As usual, feel free to ask any questions below and I’ll try to help where I can. Any corrections are welcome also (Hey, I never claimed to be perfect!).
