What is a typical weight per gallon used for aviation fuel in balance problems?

• A. 8 pounds per gallon
• B. 4 pounds per gallon
• C. 10 pounds per gallon
• D. 6 pounds per gallon

Answer: (D)

In weight and balance, you convert fuel from gallons to pounds using a standard weight per gallon, then use that weight with its arm to get the fuel moment. For aviation gasoline, the commonly used value in balance problems is 6 pounds per gallon. That means fuel weight equals gallons × 6. This simple density lets you quickly determine how fuel affects the airplane’s total weight and center of gravity.

Using 6 lb/gal is chosen because avgas density is approximately 6 lb per gallon in practical calculations, which keeps calculations straightforward and reasonably accurate for most light aircraft. If you used a heavier or lighter figure, the computed weight and CG would be off. (Jet fuel, by contrast, is closer to about 6.7 lb/gal, but many GA balance problems use 6 lb/gal for avgas.)