partition your hard drive Time Machine will automatically eat up all of the space available to it.  To limit the space available, you need to partition the hard drive that you're backing up to.  Use Disk Utility to partition your hard drive.  Remember that partitioning your hard drive will erase everything on it, so you'll need to either save your Time Machine stores elsewhere or start over again with it. Yes, but you have to partition the harddrive... Time Machine does not have any settings that allow you limit the amount of space it uses for backups, but you can work around this by partitioning your backup harddrive and setting the partition space as your destination backup location.