Need help calculation partition space

[Djard007]

I created a partition on an 1.5 TB external USB drive and cloned the 320 GB internal HDD of my notebook onto the partition. To create a partition the same size as the HDD in my notebook, I had to calculate the binary size as reported by Windows. I'm hoping someone can help be find a better way perform the calculation.

Using Win 7's Disk Management tool, I had to enter the amount of space to shrink the USB drive, in order to make room for the partition. Below is what I formulated, but surely there is a more accurate and efficient way.

Total size before shrink: 1,430,796 MB
Size available shrink space: 663,230 (free space on drive that contains stored files)
Enter the amount of space to shrink: 294,796
Total size after shrink: 1,136,000

So shrinking the drive by 294,796 gives 287,890 MB of unallocated space for the partition, just a tad larger than the target size of 286,9700 MB.

Rounding off to the nearest GB, I calculated the "the amount of space to shrink" as 294,796 MB to create a partition of 287.89 GB (287,890 MB) as follows.

Decimal size: 320,000 MB
Windows reports binary size: 286,970 MB
Size difference: 33,030 MB
Difference: 10.3219 %

But shrinking the size by 286,970 + 10.3219% (29,621) = 316,591 MB that is too large.

However, entering 294,796 MB for the amount of space to shrink creates 287,890 MB of unallocated space for the partition, which is close enough. So I figure that when entering the amount of space to shrink, I need to enter a size that is 2.72727% larger than the target size.

286,970 MB + 2.73% (7,826 MB) = 294,796 MB

Is there a better method than I used here?

 

[drtweak]

If you need to clone a partition to the end of another drive you can use Macrium Reflect after you shrink the drive down in windows. Macrium only needs enough free space for as much Data you are cloning and not the who partition size.

But if you are wondering why you can't get all the space when you shrink it is because of windows and its stupid defrag. It doesn't consolidate the drive so when you shink a drink it can only shrink down until it finds data. It will NOT move the data for you to shrink more.

You can do one of three things.

1) There are free partition programs like EASEUS and Partition Magic that can shrink drive with no issue.
2) Use defraggler to defrag and consolidate all the data to the begining of the drive leaving you much more room to shrink using windows disk management.
3) Shrink as much as windows will let you. As long as it is big enough as much data there is use Macrium Reflect to copy over that partition once you shrink it.