Richard Collins of Flying fame once did an article about the subject. I can't remember all the details but he had a formula that took gallons per hour (Rich of Peak) times price per gallon times a constant and voila you had a pretty close estimate of your cost per flight hour. I think for a retract single the constant was 2.5 to 3.0. For a fixed gear single it was about 2.0 and for a light twin it was better than 3.0.

 

Jeff Edwards

LIVP N619SJ

(too much to think about)