In this Ubuntu help wiki about DiskSpace, it is recommended to have the size of EFI partition somewhere around 100~250 MB. However, I might have a 150 MB EFI partition while it actually needs 151 MB of space!
So how to know the exact size I need to allocate to the EFI partition?
You cannot know the exact size unless:
Using my own machines as a reference, the EFI partitions on the daily workhorses are 1GB in size. The partitions exist on a storage device that is at least 512GB in size. Currently none of the EFI partitions exceed 1.8% utilisation, or 180MB (the lowest is 97MB).
Having been burned by excessively small EFI partitions in the past, I allowed the Ubuntu installation wizard choose the size of its EFI partition and have had exactly 0 issues since then.
Microsoft recommends 100 MB for its operating systems, while many Linux forums suggest more for Linux based operating systems or for any dual boot or multi booting situations.
The author of gdisk suggests 550 MiB.
As per the Arch Linux wiki, to avoid potential problems with some EFIs, ESP size should be at least 512 MiB. 550 MiB is recommended to avoid MiB/MB confusion and accidentally creating FAT16.
So, most common size guideline for EFI System Partition is between 100 MB to 550 MB. One of the reason behind this is it is difficult to resize later as it is the first partition on the drive. EFI partition may contain languages, fonts, BIOS firmware, other firmware related stuffs. There are some firmware/software that are installed into the the EFI partition instead of the data drive.
As it may be difficult to enlarge the size of the EFI partition in the future, and because many storage devices measure in the hundreds of gigabytes, it makes sense to go with something that is not the absolute minimum unless the plan is to install the OS, disconnect the device from the Internet, and run it without updates until the end of time.
