# Thread: Someone show me the maths!

1. ## Someone show me the maths!

Can someone stick up some maths to show me how much space *should* be available after formatting a hard drive.

2. nope.....pick a number less than the advertised hdd space and guess

Formatting and putting a File System on takes space...PLUS 1024x1024 bytes iscalled a Megabyte, even though its more...and 1024 megabytes is CALLED a Gig...even though its more.

ie the numbers are rounded off. So a Gig is not a real Gig at all.

think thats right

3. oh I'll wait for Agent to explain..or Kez...or Moby...or Jiff.....or ANYONE cleverer than moi

4. Originally Posted by Tifosi
Can someone stick up some maths to show me how much space *should* be available after formatting a hard drive.
This and particularly this should explain far better than my attempt at any rehash..

HTH,
S.

5. Take the amount advertised in Gigabytes, and make it into millions of kilobytes (1000 bytes to the kilobyte, just like the manufacturers do.)

So 60GB -> 60,000,000 kbytes

Then divide it by 1024, giving you the "real" megabytes:

58,593.75MB

Divide that by 1024 again gives you about 57GB. There's still filesystem overhead to go on top of that too though. Not sure how much that knocks off.

6. So there's no set size like...

i.e. formated with NTFS (figures are from my Seagates)

200gig drive will be 186GB
160gig drive will be 149GB

why divide by 1024 twice and not just the once?

7. The main reason is that HD manufactures are liars. Filthy, dirty liars.
They claim that 1 gigabyte = 1 000 000 000 bytes
It doesnt, 1 gigabyte = 1 073 741 824 bytes

So, if you have a 200gig drive, it will actually have 200000000000 bytes.

200000000000 / 1 073 741 824 (how many bytes there REALLY are in a gig), will give you 186.264514923095703125 aka, 186.26 gig

For 160 it would be 160000000000 bytes.

160000000000 / 1073741824 will give you 149.0116119384765625, aka, 149 gig

Hope that helps

8. Originally Posted by Tifosi
So there's no set size like...
No, you gotta perform the simple calcs just like Kez & I said to get the actual capacity.

Of course, depending on the cluster size of your chosen file system, you're gonna see more/less usable capacity also, depending on the number/size of files you store.

S.

EDIT: Well said Agent..

9. Basicly, we are being screwed over by 73 741 824 bytes for every gig that they sell us.
It really winds me up. I wish i could get enough people to write and complain to trading standards, all together.
Do you think they could sell 1 litre bottles of water, but then say at the bottom of the label "1 litre = 750ml" ?
Simply redefining the gigabyte to a different number than it really is, is bs.

10. the rule of thumb i use is take 10% of the claimed capacity of the drive off, that's roughly what you get after you've formatted it if you use the default NTFS cluster sizes and whatnot. Usually 10% is a little more than what you do lose, but that way when you see the capacity in your My Computer you get a little smile as you have more space than you thought you were going to

Also, partitioning a drive into a lot (i.e. more than 3 or so) partitions means the cumulative loss after they're all formatted is greater than one big partition after it's formatted.

Thing is, in decimal terms a gigabyte IS 1,000 megabytes since mega just means x1000 so the HDD manufacturers can't really be said to be lying about their products' capacities... But yes it gets on my moobs as well...

11. thanks guys

12. Originally Posted by Agent
The main reason is that HD manufactures are liars. Filthy, dirty liars.
They are not lairs at all, not when it comes to hardrive capacity. They list the literal truth. If some oen is fooled by it, that is thier problem.

A leter is 1000ml not 1024ml.1,000 bytes is a kilobyte, 1,000,000 bytes is a megabyte and, 1,000,000,000 bytes is a gigabyte, at least acording to SI and IEEE. In this way hardware makers are actually more correct than software.

Simply redefining the gigabyte to a different number than it really is, is bs.
The your problem is with software makers, not harddrive makers. The volumes listed for various harddrives are technically correct, the volumes reported by most software is technically incorrect.

13. The problem is not with software makers at all, the problem is the computer works in binary. Thats what the units should be in. Two to the power of something.

TiG

14. Someone (I think it might have been DELL) did try to take Sony to court over this - don't think they won though.

15. Originally Posted by oralpain
A leter is 1000ml not 1024ml.1,000 bytes is a kilobyte, 1,000,000 bytes is a megabyte and, 1,000,000,000 bytes is a gigabyte, at least acording to SI and IEEE. In this way hardware makers are actually more correct than software.
No its not. Mega, giga and kilo may be defined in other cases as 10^6, 10^9 and 10^3, but Megabyte, Gigabyte and Kilobyte are and have been difined as 2^20, 2^30 and 2^10 since the computer existed.
They have taken "de facto" naming and decided to change it to mislead the consumer. Before the HDD manufacturers changed it, everyone used the correct convention. They diverged from the accepted standard at the time and it was them alone. Therefore they are incorrect

No its not.
Yes, it is.

Using kilobyte for 1,024 bytes is factually wrong, even with computers. It was started as an abreviated and unofficial way of simplifing things. It is still incorrect and it never was official. Hardrive makers never changed a thing.

The prefixes officially mean the same thing regadless of what they are infront of. Kilo is always 1000, mega is always 1000000, ect, wether it's infront of a gram, liter, ohm, byte, ton, whatever.

Originally Posted by TiG
The problem is not with software makers at all, the problem is the computer works in binary. Thats what the units should be in. Two to the power of something.
Then both harware makers and software makers need to change to Kibi, Mebi, ect. Kilio, mega, are base 10.

http://en.wikipedia.org/wiki/Binary_prefix

http://www.iec.ch/zone/si/si_bytes.htm

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