The only way I know if is to delete the sheet, SaveAs the file to a new dummy file, and compare the sizes of the two files. The difference is the size of the deleted sheet. Just be careful not to accidentally save the file, overwriting the one with the sheet.
I don't know of another way. But if you must do this a lot it would certainly be possible to write a macro that would do the sheet delete, save and size comparison and give the result. This would save you from having to perform the steps manually. It could also be designed to restore the original file.