This is another 'Microsoft Quirk'.....

Word allows you to alter the measurements within the program.......HOWEVER........Excel and PowerPoint take their settings from WINDOWS.

Go to Control Panel > 'Regional and Language Option'

On the Regional Options tab at the top of the window you will see a drop-down box with a country showing - I presume yours is saying 'English (United States)'. If you change it to 'English (United Kingdom' and click on Apply, go back to Excel (or PowerPoint) and VOILA! measurements are now in centimetres!!!!

......MICROSOFT!......Heaven help us :?