You may estimate ‘averages,’ but should prepare for some extra.
Start by checking your car’s mileage at mpgbuddy.com. Ever individual car is different, but this site will set expectations. (note: if you keep detailed records of gas purchases and mileage, you could compute your car’s mpg).
Now divide miles / miles-per-gallon to get the number of gallons of gas you will need (perhaps less or more than one tankful)
Lastly multiply the miles by dollars-per-mile (note: miles cancel) to get the estimated dollars.