Three flash drives I have on hand:

  64 GB:
  Disk /dev/sdi: 60 GiB, 64424509440 bytes, 125829120 sectors
  Units: sectors of 1 * 512 = 512 bytes
  
  32 GB:
  Disk /dev/sdi: 28.9 GiB, 31037849600 bytes, 60620800 sectors
  Units: sectors of 1 * 512 = 512 bytes
  
  8 GB:
  Disk /dev/sdi: 7.2 GiB, 7743995904 bytes, 15124992 sectors
  Units: sectors of 1 * 512 = 512 bytes

Apparently they're just kinda sorta close to what they're sold as, and they're not accurate in base10 or base2.

Thanks for sharing those numbers. Definitely closer in base 10, but not as close as mine were.

The 32 GB one is disturbingly off. 31 GB would have been more honest. If the spare sectors required go up more then they'll have to adjust their marketing numbers and maybe we will see 30 GB, 60 GB, or 120 GB flash drives sold.

Actually, there is little consistency in the advertised size of flash drives.

USB sticks are predominantly sold in base-2 sizes (32, 64, 128 GB etc). In fact, I don't think I've ever seen a 30GB or 100GB usb disk.

How SSD sizes are advertised depends entirely on the manufacturer, and even manufacturers don't use a single base: Samsung's EVO series are advertised in multiples of 10 (250, 500GB), while its PRO series use sizes in multiples of 2 (256, 512GB). Sandisk uses 120 GB, 240 GB sizes. I'm not even sure if all those sizes are supposed to represent base-10 or base-2 prefixes.

But those "32", "64", etc., numbers are times 1,000,000,000 bytes.

That isn't the case with some of the ones that I have on hand. This "128GB" stick is "128GB" as a multiple of 1,069,285,120. Presumably, it's 128GiB less an allocation of spare blocks and the filesystem overhead.