I am presenting tabular data. One column represents the size of a shape, however the shape itself may be a line, area, or volume. So size values can be in units mm or mm2 or mm3. However, I only display the values, not the units, in the table. For example:
| Type | Size (mm) |
|--------|-----------|
| Line | 123.4 |
| Area | 456.7 |
| Volume | 234.5 |
There is a lot of confusion from users about the use of "Size (mm)". Some users will tend to only generate Area shapes, so they think it's a mistake that it says "mm" and not "mm2", etc. However, any user can make any shape and it is common for a table to be filled with different shape types.
I like putting "(mm)" in the heading because it conveys at least that the data is in some dimensions of millimeters, but this is also the source of the confusion.
Do I just remove "(mm)"? Add a tooltip? The table has a lot of columns already, so breaking it up into separate columns isn't a great option either -- and besides, all the values represent the same concept of "Size", just in different dimensions. I also don't want to add the units to the table cells, because that would prevent someone from copy/pasting the data into Excel.
Any good ideas for a solution to this?