h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

I'm trying to estimate potential broadband usage. Using an online calculator I got 1712 MBs but the plans are all in GBs. SO how

Sorry, my browser wouldn't let me type anything further in the text box

So, how many MBs in a GB?

http://bugclub.org/beginners/math/byte.html

he fundamental data unit of personal computers, a byte is eight contiguous bits. The byte is also the basic unit of measurement for computer storage, storing the equivalent of one character. Computer architecture is based mostly on binary numbers, so bytes are counted in powers of two (which is why some people prefer to call groups of eight bits "octets"). The terms kilo (in kilobyte, abbreviated as K) and mega (in megabyte, abbreviated as M) are used to count bytes (even though they are misleading, since they derive from a decimal base of 10

Kilobyte 2^10 1,024 bytes or 8,192 bits
So, a kilobyte is actually 1,024 (210) bytes. To distinguish between a decimal K (1,000) and a binary K (1,024), the IEEE has suggested using a small k for a decimal kilo and a capital K for a binary kilo. In international English, outside the U.S.A., the equivalent unit is sometimes seen as "Kb" or "kbyte."

Kilobyte 10^3 or One thousand 1,000
Abbreviated as K or KB also seen as Kb kbyte. A unit of measurement equivalent to one thousand bytes of computer memory or disk capacity. For example, a device that has 256K of memory can store approximately 256,000 bytes (or characters) at one time. In decimal systems, kilo stands for 1,000, but the computer world is based on a binary system of twos instead of tens.

Megabyte 10^6 one million 1,000,000
abbreviated as M or MB, A million bytes or one thousand kilobytes.

Gigabyte 10^9 one billion 1,000,000,000 Abbreviated as G or GB. A unit of measurement approximately equal to 1 billion bytes. A gigabyte is used to quantify memory or disk capacity. One gigabyte equals 1,000MB (actually 1,024 megabytes).

Terabyte 10^12 one trillion 1,000,000,000,000
A unit of memory measurement equal to approximately one trillion bytes (actually 1,099,511,627,776 bytes). One terabyte is equal to 1,000 gigabytes or 1 million petabyte

Petabyte 10^15 one quadrillion 1,000,000,000,000,000
A unit of memory measurement that is 250 bytes (equal to 1,125,899,906,842,624 bytes or 1,024 terabyte). It's used primarily in distributed storage solutions and within major enterprise solutions.

Thanks. I'll keep that for further reference

In the end I typed >how many MBs in a GB< into google and got 25,000 hits, so I guess it's a reasonably common question.

Yes it is a common question...I've been working in IT for a very long time...so it seems like a easy question, but I remember learning about the Gigabyte for the first time perhaps 15 years ago.

I used to worry about managing computers that had no memory and consisted of mere wiring on bread boards and card sorting devices, then servers with 60 Megabytes of storage and workstations with 10.

I just bought a home computer for less than 700 Euros that has 250 Gigabytes of storage.

But, I should have just said 1,000 megabtyes = 1 gigabyte.

Sorry. Good luck

Much easier way to estimate broadband usage is to ask the community of course.

I'm a fairly heavy user, considering I only use it out of a 9-5 job. 2-3 hours surfing a day, 5-6 hours of internet radio a month, perhaps a couple of hefty downloads a week comes to about 2GB a month. When I hooked up for some P2P I got through 7.5GB in a fortnight!

B

Fred, it was still a useful answer

B, did you mean 'heavy' use?

That's a good idea, getting an idea of researchers' usage.

Here's the calculator I was using (although this is not the company I am considering): http://www.telecom.co.nz/chm/0,5123,203152-202343,00.html

I find they tend to underestimate. You'll note it's assuming you're not going to _upload_ anything.

B

Is this in connection with NTL's upgrades and their threat to really impose a hard cap this time?


Incog.

What's NTL?

You just made my day...

If you don't know NTL the ISP,telco and cable TV company you are missing nothing.

Frankly there are many who would wish they had never heard of NTL...

Anyway I thought that this inquiry about GB's might have something to do with the BB CAP issues that is exercising some NTL users.My mistake.

I live in New Zealand, Incognitas. I could tell you about how cr*p the telco companies here are if you like

To simplify the post from Fred...

In the normal course of metric numbers:

1k (kilo) = 1000 units
1M (mega) = 1000k, or 1,000,000
1G (giga) = 1000M, or 1,000,000,000
1T (tera) = 1000G, or 1,000,000,000,000

So you see, each letter up the scale represents a 1000-fold increase. But since computers are binary, 1000 is a messy number. 1024 is better, because it's a power of 2 (2^10, as said before). Therefore, in computer parlance:

1kB = 1024 bytes
1MB = 1024 kB, or 1,048,576 bytes
1GB = 1024 MB, or 1,073,741,824 bytes
1TB = 1024 GB, or 1,099,511,627,776 bytes

So, when you really, really need to know how many MB you've got available, divide by 1024. Otherwise, as you can see from the charts, 1000 is close enough for government work. Just move the decimal over 3 places and you've got a pretty good estimate.

And a slight correction to Fred: kb is not the accepted shorthand for kilobytes. The small "b" stands for bits, and the large "B" stands for bytes. Therefore, kb stands for kilobits. This is quite an important distinction when we are discussing data transmission rates, since they're usually measured in bits per second. Anyone expecting those rates to be in bytes per second would be dismayed to find their downloads working 8 times slower than they expected (since there are 8 bits in a byte).

Thanks Blather.

Does the 1000 vs 1024 thing explain why my 100MB zip discs in fact only fit something like 94 or 95MB of info on them?

yup!

So why don't they call it a 95MB disc? (or whatever it actually is)

Because 100MB sounds like more. And they have a reasonable defence against claims of false advertising.

B

When your system tells you a file is 100MB, it's calculating the bytes by powers of 1024, so it's accurate. For example, I just displayed the properties of a file, and under Size I get: 770KB (789,024 bytes).

So, on the question of the storage media, it depends on where the error is being made. If you're looking at your files and seeing the sizes reported in kB, and you're just moving the decimal over three places to convert to MB, then the storage media can hold 100MB, but you're making the mistake in conversion. If your application is reporting the sizes in MB, then the fault is with the manufacturer, for being deliberately misleading.

And they can't really justify saying that their capacity claims are in decimal, and not binary. "Megabytes" is a term that is meaningless in decimal. And if they don't understand binary, they shouldn't be making computer products.

The OS application measures in both MB and bytes eg one folder I was trying to save to ZIP ended up being 93.8MB (96,620,775 bytes).

That doesn't add up right though does it? 93.8 multiplied by 1024 = 95232 KB or 95,232,000 bytes.

So if I go off the bytes rather than the MBs I should have a more accurate idea of what's going to fit on the ZIP? The numbers still don't make sense though.

For floppy disks, Zip Disks, Hard Disks and in fact all removable/non-removable media, the size quoted is the size when the media is in its initial unformatted state. The size it eventually ends up all depends on what file system type it is given when formatted. The formatted capacity gets even smaller if you decide that you want multiple partitions on the disk.