If adding one cell value is acceptable: enter the conversion factor in any empty cell (even on another sheet), select Paste Special, and select the approrpriate calculation below of Transpose.

If not: then you'll have to create a macro that applies a pre-defined arithmetic operation on every cell in a defined / selected range.

If adding one cell value is acceptable: enter the conversion factor in any empty cell (even on another sheet), select Paste Special, and select the approrpriate calculation below of Transpose.

E.g., to convert between inches and centimeters:

1. enter the factor 2.54 in an empty cell;

2. copy that cell;

3. select the values to convert;

4. Menu Edit -> Paste Special;

5. Under Operations, select the arithmetic operation to use; for in -> cm, select multiply; for cm to in, select divide:

   

Without any modification of the sheet's content: then you'll have to create a macro that applies a pre-defined arithmetic operation on every cell in a defined / selected range.