Back when I was at school a Megabyte (MB) was 1,024 Kilobytes (KB) or 1,048,576 Bytes. Well nowadays hardware manufacturers have a different IEEE take on what a Gigabyte is. For users like you and me, a Gigabyte is 1,073,741,824 (1024^3) bytes but for the manufacturer it’s 1,000,000,000 (1000^3) bytes. This means that the Gibibyte (binary) is the new Gigabyte and the Gigabyte is now … metric?

Needless to say I’ve been caught out a few times as to how much data you can actually burn onto DVD-5 and  DVD-9 media without getting the “Not enough free space” message. Burning TrueCrypt data files and WinRAR archives, I wanted to get the file size right when it came time to archive to DVD.

Pretty much most DVD-5 packaging touts 4.7 GB available, but as we well know this is based on the manufacturer’s Gigabyte definition (Base-10), not a computer science based Gibibyte definitions (Base-2). Your standard DVD+R actually ends up with 4.377 GiB (~2,294,800 sectors) and a DVD-R with 4.382 GiB (~2,297,400 sectors) with each sector having 2,048 bytes.

To be on the safe side, I’ve been creating 4.377 GiB archives which will fit on both DVD+R and DVD-R media. This means when I create my files, I’m limited to:

• 4.377 Gigabytes, or
• 4,482 Megabytes, or
• 4,589,617 Kilobytes, or
• 4,699,767,963 Bytes

Now go and burn your downloaded movie library to DVD you crazy kids! :p