Google Calculator

   Google Calculator
     < http://www.google.com.au/help/features.html#calculator >

   Google search engine has a built-in calculator function.  Just enter
   a formula in the standard Google search box and it returns the answer.
   Apart from numbers and arithmetic symbols, it also understands units
   of measure, conversions and some constants.

   A couple of example calculations:
   * Approximate Volume of the Earth
     < http://www.google.com/search?q=%284%2F3%29+*+pi+*+radius+of+earth%5E3 >
   * Something much simpler: 2+2
     < http://www.google.com/search?q=2%2B2 >