I need some help on determining how much fuel I need to get to my destination. I usually just guess how much fuel I need and most of the time I am wrong. Is there a formula or something like that so I will know exactly how much fuel I need to get to my destination?

This is just from the light-GA side. I don't know how the bigger birds work it).There's not really much of a formula for this. The aircraft's POH will have the fuel burn for different cruise regimes such as Best Power 75%, Best Endurance 65%, and Best Endurance 55%. On an E-6B flight computer (about $8-30 depending on paper or metal) you would put the 60 mark under the burn rate and read the fuel usage over the time you've calculated for cruise. For fuel use in climb or decent, you would use the tables or charts (which ever it has) in the aircraft's POH. Added together, you'd have your total expected fuel required.For example, the Piper Warrior III burns 9.1 gallons per hour in cruise at 65% Best Endurance (full throttle and mixture leaned until RPMs are at the mark determined in the POH for your altitude and temp).I don't know if you can find that kinda information online. I do know that POHs aren't ussually cheap to buy.----------------------------------------------------------------John S. MorganReal World: KGEG, UND Aerospace Spokane Satillite, Private 130+ hrs.Virtual: MSFS 2004"There is a feeling about an airport that no other piece of ground can have. No matter what the name of the country on whose land it lies, an airport is a place you can see and touch that leads to a reality that can only be thought and felt." - The Bridge Across Forever: A Love Story by Richard Bach

You know what I've done? I've made a spreadsheet of the aircraft I use. On the sheet I have takeoff fuel (in #), landing fuel, and distance. The difference between T/O and Landing fuel is the fuel used. Divided by the distance flown, you get #fuel/mile. You can setup Excell (or your favorite spreadsheet) to calculate that number.I have a few pages (one for each aircraft), and I flew a bunch of flights (like 3-5 per aircraft) to get a good average (which your spreadsheet can calculate as well) per aircraft. You end up with a number (# fuel/mile). For example, my Piper Aerostar gets 1.18#/mile. When I then calculate how much fuel I need for a 200 mile flight, I multiply the 1.18# fuel/mile number times the distance (200 miles) to get the number of # of fuel I need to load on the aircraft.This number then gets modified for current sky conditions (bad weather = more fuel) and whether I'm flying an AVSIM.COM racing leg (requiring the highest speed, or least amount of fuel) or just putzing around.This speadsheet works well for me. I would add about 20-45 minutes of extra fuel to your loadout so that you will have some extra available if you need to divert to another airport. I calculate this by adding a few extra miles to the distance that I will fly (ie: 20 minutes extra fuel @ 160kts = 53 more miles. Calculate this as 20 minutes = 1/3 hour. 160 kts divided by 3 = 53 miles. 45 minutes = 3/4 hour. 160 kts divided by 4 times 3 = 120 miles). The extra "miles" gets added on to your destination distance. For example, with 20 minutes reserve, a 200 mile trip would be calculated as a 250 mile trip for fuel planning purposes. Don't forget that your max speed (330 kts GS in the Aerostar) does not get added to your reserve fuel planning since you are not travelling at 330 kts GS when this number becomes critical. You are probabally at lower altitudes and approaching the final airport at a lower speed. I use 160 kts for the Aerostar. This gives me a huge margin for error but I have that extra fuel 'just in case'. This method works well for me, but in REAL LIFE you would not use it, I don't think. In Flight Sim, the Flight Planner calculates the required fuel, but I ignore it completely now. I use my spreadsheet exclusively, since it has 'real-world' numbers, numbers I've obtained in actual Flight Sim time.I hope this helps you out. It took me a while to get this going. I used to just fill the tanks. With the FSD-International aircraft I use (*shameless plug*), my fuel useage is tracked and accumulates $$$ data. So I try to limit the fuel I use, and this spreadsheet helps.For the RTW race (you know about the Round-the-World race, right?), fuel planning is very important because the less fuel you carry, the faster you can fly, and more speed = better racing results.Good luck!