Well, i will tell you i have never downloaded those calculators. I just fly to an area and either:
1) Do fly arounds till lose enough fuel
2) Go to aircraft options and just get rid of the fuel
3) start with just enough. (make one trip to a particular place with 100% fuel and when you get there see how much you have left. Subtract the from the 100% and you will know the exact amount of fuel you'll need for your next trip to that airport.)
4) enable unlimited fuel and just get rid of all fuel. That should work.
