Understanding CD DVD and USB Flash Drive Capacity in Bytes, KB, MB, and GB

CD DVD and USB Flash Drive Capacity

Comparison chart showing common capacity for CD/DVD and USB flash drives.

It's important to know the actual data size capacity for CD/DVD or USB flash drives. Some of the documentation is confusing because the metric system is 10 based and a KiloMeter sounds a lot like a KiloByte but a KiloMeter is 1000 meters, while a KiloByte is 1024 bytes.

To make matters worse, sometimes product documentation, marketing material, or specifications may refer to Gigabytes (GB) or Megabytes (MB) but you're not sure if they got to those values using metric 1000 based conversions or the proper 1024 computer binary based conversions (2,4,8,16,32,64,128,256,512,1024). For example, DVD-R is often said to have a capacity of 4.7 GB but it really only has a capacity of 4.377 GB (4,700,000,000 bytes).

The following table explains the actual data capacity of the some common CD/DVD and USB Flash Drive sizes. Some of the USB flash drive information may vary depending on the chip manufacturer of the USB thumb drive, and whether it's formatted FAT32, NTFS etc.

Product Bytes KB (Bytes / 1024) MB (KB / 1024) GB (MB / 1024)
CD-R 737,280,000 720,000 703 0.687
DVD-R 4,700,000,000 4,589,843 4,482 4.377
USB 512MB 504,078,336 492,264 480 0.467
USB 4GB 4,018,593,792 3,924,408 3,832 3.74
USB 8GB 8,036,294,656 7,847,944 7,664 7.48
USB 16GB 15,633,997,000 15,267,575 14,909 14.56

USB capacity.  Flash Drive Packaging Prices.