set the size of time machine backups

No, not natively to your initial question.

One must originally provision a Time Machine drive that is 2.5 - 3x the size of the startup drive. Time Machine is autonomous and will eventually remove some backups if daily, weekly, and monthly consolidations meet its criteria for that purpose. However, Time Machine does not remove the same quanta as the current backup requires, and if the available drive storage would be exceeded, then Time Machine will fail to backup. Never manually try to do Time Machine's thinking for it and remove backups yourself.

Hi,

There's no way to set anything relating to size, but you can adjust the frequency with third party software such as TimeMachineEditor.

ln10e wrote:

Is there a way to set the size of your time machine backups along with frequency the backups are ran

Q - " Is there a way to set the size of your time machine backups "

A - No. The size of the Time Machine Backup is totally depended on the amount of files changes that have occurred since the last time Time Machine was last set to preform a Snap Shot of those changes and then moved to the external Drive.

Manually deleting Time Machine Backups runs a very high risk of corrupting the index files that TM Backup using to keep track of the Snap Shots on the External drive.

If that were to happen, the entire series of Backups on the drive would be corrupted and totally useless.

That would require Erasing the Drive to zero and starting a Time Machine Backup as New.

ln10e wrote:

Thank you for the reply. So there is no where to set the backup say for 400 gig and when it hits that size delete the oldest backup? Is there a way I can delete the oldest backups?

You're welcome.

Short answers: no and no. To the second question, TM is supposed to do that automatically; sometimes it works, and sometimes it's not able to.

Time Machine works as if it is on its own external drive and is able to use all the free space.