There are probably some sites around on the Web which will give indicative figures (you can also buy a book, one variety of which is published by AFE) which will give *indicative* data. The only truly accurate information is in the Pilots Operating Handbook for your aircraft - the results of the aircraft weighing, etc will be in there, etc; this will be different for every aircraft.
Sorry if this seems unhelpful, but the only legitimate source is the POH.