SanDisk SSD not showing accurate storage reading on Mac

Hi AppleQ8,

Thanks for the screenshots. It appears that there are over 160,000 items on the drive, which may explain the discrepancy. Different file formats may have a different cluster or allocation unit size, which means the actual amount of space taken by data may vary based on the number of distinct files. It is expected that the total data size will be smaller than the size on disk.

Was the disk originally formatted using Disk Utility on Mac, or from within Windows? If you used Windows, we can recommend formatting using Disk Utility and copying the data again, to ensure optimal compatibility with macOS.

Otherwise, we could recommend formatting the drive using a different format, such as macOS Extended Journaled or APFS, then transfer your files and verify that the size on disk is different, although this would prevent the drive from being used with Windows.

Take care!

Hi AppleQ8,

Welcome to Apple Support Communities! We're glad you've reached out for help with this behavior you're seeing. Let's get to the bottom of this together.

To start, let us know more about what's going on. Where is it that you're seeing this large file size? Which version of macOS are you using on your computer? This can be found under Apple menu () > About this Mac.

Have you had an opportunity to restart your computer since noticing this behavior? If not, let's do so now. Here's a guide with the recommended steps for a standard restart:

Log out, sleep, wake, restart, or shut down your Mac - Apple Support

We'd like to share the following link with more information as a reference. Let us know if you continue to see more storage space being used than is present in the sum of individual files:

Get file, folder, and disk information on Mac - Apple Support

Have a great day!

jcasapple wrote:

Thanks for the screenshots. It appears that there are over 160,000 items on the drive, which may explain the discrepancy. Different file formats may have a different cluster or allocation unit size, which means the actual amount of space taken by data may vary based on the number of distinct files. It is expected that the total data size will be smaller than the size on disk.

This can possibly be the reason. Different size drives require different allocation cluster sizes plus different utilities and operating systems may use different allocation units as well.

It is usually best to use Disk Utility to erase a new drive even if you will be using the "same" exFAT file system on the drive due to the differences just noted especially since macOS has a much more limited understanding of the different allocation cluster sizes. That means the allocation cluster sizes used by SanDisk may be completely different than those used by Samsung.

Also just because something comes from the factory pre-formatted does not mean it is formatted correctly, nor does it mean the drive is empty. A lot of drive manufacturers tend to install utility software on a hidden area of a drive.