Note: You can tick the box option "Display Fuel qauntity as Weight" when setting the fuel / payload in FS2004, this will provide you with your fuel in the units LBS (Pounds) which you use for the FlyNet Client !
This fuel calculator below is highly endorsed by myself as it is very accurate:
Updated Fuel Calculator - This freeware program written by WestWind pilot, David Liu, A9144, KORD Hub, calculates the fuel needed for a trip. IFR reserves can then be added manually. It uses the values stated in the WestWind POH to calculate the total fuel requirements.
Download it here now !
How to use it in 8 simple steps:
1 ) Find out your distance (total) from your Navigatoin Log before clicking the fly now button within FS.
2 ) Come onto Desktop (Either hit windows key or alt + tab together or even ctrl + esc)
3 ) Open the fuel program
4 ) Choose the aircraft you are in
5 ) Enter the distance and click on calculate
6 ) You will now know how many Gallons you need to enter into each Tank!
7 ) The total fuel amount is in Pounds NOT Gallons !
8 ) Enter the needed fuel ... consider giving yourself extra (I usualy give myself about 5 - 10% depending on weather)
For example:
Say I choose B753 (4 above)
Enter a distance of 290nm (5 above)
I click on calculate (6 above) and get the following:
I then simply enter the amount into my center tank at 2247 Gallons. I then round it up to the nearest 5% / 10% depending on weather and nereast emergency.
Hope you find this as useful as I do, though tbh I am going to make my own in C++ towards the backend of summer so keep a look out!
I'll do it after uni 
