Trying to format a USB drive in Ubuntu? So was I. The following instructions were the most helpful solution I could find.

Determine where your USB is mounted.

1. Insert your USB
2. Right-click the icon, properties, volume tab: take note of the mount point. It might be, for example, /media/USB
3. Open a command prompt, type

mount

One of the lines (probably the last one) will contain the mount point. The start of the line geves you the device name, e.g.
/dev/sdb1 on /media/USB type vfat (rw,nosuid,nodev,shortname=mixed,uid=1000,utf8,uma sk=077)
In this example, the device is /dev/sdb1

Format the drive

In a command prompt, type:

sudo umount /dev/sdb1
sudo mkfs -t vfat /dev/sdb1
sudo eject /dev/sdb1

Now take out the USB and reinsert it, so that it gets mounted again.

Your USB should be ready to go!