When File Explorer refuses to format your USB flash drive — "Windows was unable to complete the format", wrong capacity shown, or a stubborn leftover partition from a bootable installer — the Command Prompt is the tool that still works. Here is the practical version: DiskPart for the hard cases, and the plain format command for everyday use.

Pick the file system first

  • exFAT: the default choice for modern flash drives. No practical file-size limit, readable on Windows, Mac, and modern phones.
  • FAT32: maximum compatibility with old devices (TVs, printers, car stereos) — but a single file cannot exceed 4 GB. I verified this myself: a 4.5 GB test file copied to a FAT32 image was rejected instantly with File "VIDEO4K.MP4" too big. The exact limit is 4,294,967,295 bytes.
  • NTFS: only if the drive stays on Windows and you need encryption or file permissions.

Method 1: DiskPart (the thorough way)

Open Command Prompt as administrator, then run these lines one by one:

diskpart list disk select disk 1 clean create partition primary format fs=exfat quick assign exit

Replace 1 with your flash drive's number from list disk — and double-check it with detail disk before typing clean. The clean command wipes the partition table of the selected disk, so picking the wrong disk can erase an internal drive. In my own simulation, zeroing the first 1 MB of a test image made the old file system instantly unrecognizable (non DOS media), which is exactly why you back up first.

Quick format is nearly instant: in my test, FAT32 formatting took 0.08 seconds and exFAT 0.03 seconds on a 64 MB image, because quick format only rewrites the file table. A full format is a different story — roughly 13 minutes for a 64 GB drive over USB 3.0, or about 71 minutes over USB 2.0.

Method 2: the plain format command (the fast way)

If the drive is healthy and already has a drive letter, one line is enough:

format E: /fs:exFAT /q /v:USBKU

Replace E: with your drive letter. /q means quick format; without it you get a full format. /v:USBKU sets the volume label.

Common errors

  • "Windows was unable to complete the format" — use the full DiskPart method above. If that fails on two different computers, the controller is likely dead.
  • "The disk is write protected" — check the physical lock switch first, then run attributes disk clear readonly in DiskPart before clean.
  • Format stuck at 0% — usually bad sectors or a worn-out chip. Wait 5–10 minutes, then try a full format; if that fails too, the drive is at the end of its life.

One last check after formatting: a 64 GB drive should show about 59.6 GiB in Windows (the 6.9% gap between decimal GB and binary GiB is normal, not a fake drive). Copy a file onto it, unplug, plug back in, and confirm the file is still readable.

The full Indonesian tutorial — with the complete step-by-step DiskPart walkthrough, my simulation results, and more troubleshooting — is on my blog: Format Flashdisk dengan CMD (Diskpart) di Windows 10/11. If your drive shows the wrong capacity, check whether it is genuine first: how to check if a flash drive is fake.