Hi Rob, yes you can, although bear in mind that it is only an estimate (and assumes you have done all the appropriate training).
There is a calculator on the RW site
http://www.runnersworld.co.uk/general/rws-race-time-predictor/1681.html
or this one
http://www.mcmillanrunning.com/mcmillanrunningcalculator.htm
(among others)