You’ve already seen how high gas prices are affecting your bottom line. Now you can calculate exactly how much. A new tool available on the Automobile Club's Web site calculates how much you will pay for gasoline on a trip using real-time average fuel prices. The Fuel Cost Calculator, available at www.fuelcostcalculator.com, computes the fuel costs for trips using a vehicle's model and year, as well as regional gas price averages updated daily. To use it, go to www.fuelcostcalculator.com and click on "More News," then "Gas Price Information," then "Fuel Cost Calculator." Select the areas closest to your departure and destination, then select your vehicle's make, model and year. The calculator will then figure out the approximate trip mileage, fuel usage and gas costs, both one-way and round-trip. For multiple destinations, click on "Start Over" to estimate gas costs for each leg of the trip. Real-time average fuel prices are updated daily on the site by Oil Price Information Service, the nation's most comprehensive source of petroleum pricing information.