Convert-Me.Com - online units conversion

A converter is needed that takes inches or cm and applies the map scale (eg, 1:25,000) as well as the units conversion to give the actual disance in miles or Km, and the inverse.

This means that a distance measured on the map in (say) inches can be converted to the actual distance in miles. And the reverse means that a distance quoted for a mapped feature in (say) miles can be converted to a distance in inches. So if it says "The hut is located 4 1/2 miles SSW of the railway bridge" and the map scale is 1:25000, then I know to look for it on the map at a distance of ?? inches. Or, if I find that two features on the map are 9.5cm apart, and if the map scale is 1:40,000 then I know that I will be walking ?? km from one to the other.

In the manual on page 7-19 it says the current map scale is indicated by showing the centimeterkilometer and centimetermile ratio.

By default, I presume, it is shown in kilometers, how do I show it in miles like it says, is this possible and if so how, thanks.