Planning densities
U.S. flight-planning practice, reflected in the Pilot’s Handbook and in most POH weight-and-balance examples, uses
- 100LL / avgas: 6.0 lb per US gallon
- Jet-A / Jet-A-1 / JP-8: 6.7 lb per US gallon
- Jet-B / JP-4: 6.4 lb per US gallon
- JP-5: 6.8 lb per US gallon
So 50 US gal of 100LL is 300 lb, and 50 US gal of Jet-A is 335 lb. Those figures are for planning, not a fueler's measured density.
Temperature
When you opt in, the page starts from a typical 15 °C specific gravity (about 0.72 for avgas, 0.80 for Jet-A) and applies a linear expansion correction ρ(T) = ρ15 (1 − α (T − 15 °C)). Warm fuel is lighter for the same volume; cold fuel is heavier. Use a measured density when the weight matters to the kilogram.
Sources
FAA Pilot’s Handbook of Aeronautical Knowledge (fuel-weight planning figures); ASTM D910 / D1655 typical specific gravities. For trip fuel, reserves, and endurance, use the fuel planner, which uses the same 6.0 / 6.7 planning densities.
Frequently asked questions
Why is 100LL planned at 6.0 lb/gal when the specific gravity is about 0.72?
0.72 times the density of water is about 6.0 lb/US gal, which is why the planning figure and the typical SG agree at 15 °C. The book figure is rounded and is used year-round unless you apply a temperature correction or a measured density.
How many kilograms is a litre of Jet-A?
At the 6.7 lb/US gal planning density, about 0.80 kg/L. Temperature and the actual batch will move that number.
Are US gallons and imperial gallons the same?
No. One imperial gallon is 4.54609 L, about 1.201 US gallons. This page converts both.