How do I format a usb drive on a PC or Mac? I have a USB drive that was formatted for a Mac and now I want to use it for a PC. How can I do to make it?
It’s quite simple. Note that reformatting the thumb drive will erase all it’s contents. 


Open Disk Utility. It’s located in the /Applications/Utilities folder. Or just type in “Disk Utility" in Spotlight. 
Select the drive (not the volume), and click the “Partition” tab.
Select “1 partition” from the drop down. Then click Options… > select “Master Boot Record” as the partition scheme
Format: exFat
Give it a name. 
Click apply, and you are done. 


Notes:


If you want the USB drive to be universally compatible, format it as exFAT/FAT32. The standard nowadays is exFAT. It supports files of up to 16 exabytes in size. FAT32 only supports 4 GB files. Additionally, in a windows environment, the FAT32 filesystem is subject to more fragmentation. 
If you want to use it exclusively on your PC, reformat it as NTFS in Windows on your PC (you can reformat as exFAT and FAT32 in Windows as well). An NTFS filesystem is read only in an OS X environment. OS X’s Disk Utility does not offer this as an option.
Others may suggest just to click the erase tab. This does not properly reformat the disk since the partition table isn’t modified.