Check the SSD capacity listed by the manufacturer
Convert the advertised size from decimal to binary if needed
Subtract space used by the operating system and recovery partitions
Subtract formatting and file system overhead
Check the usable capacity shown in disk management or storage settings
Compare the drive’s raw capacity to the capacity reported by your device
Account for reserved space used by firmware or overprovisioning
Verify whether the SSD is shared with other partitions or volumes
Use the formula: usable space = advertised capacity – system overhead – reserved space
Confirm the exact model number and look up its official specifications