Most hard drives made after 2010 have at least a 500-gigabyte capacity, with some as large as 6 or 8 terabytes. Aside from some laptops, which may have 250-gigabyte or 320-gigabyte hard drives, most hard drives are only available in increments of 500 gigabytes or 1 terabyte.
While hard drives always list their space as an even amount of terabytes, there's actually a slight difference in the amount of usable space. For example, if a hard drive has 1 terabyte of space hard drive, you can only use about 931 gigabytes. This is because a gigabyte is actually 1024 megabytes, which means it doesn't go into a terabyte 1,000 times evenly.