Weight & Balance Calculator
How It Works
This weight & balance calculator uses established formulas to provide accurate results.
The basic rule:
- Fuel Weight = Gallons x 6 lbs/gal (avgas)
- Moment = Weight x Arm (distance from datum)
- Total Moment = Sum of all individual moments
- CG = Total Moment / Total Weight (must be within envelope limits)
Results are estimates. Consult a professional for critical decisions.
Frequently Asked Questions
Why is weight and balance important?
An aircraft loaded outside its weight and balance limits is dangerous and potentially uncontrollable. If the CG is too far forward, the aircraft needs excessive back pressure on the yoke, stall speed increases, and landing can be difficult. If the CG is too far aft, the aircraft becomes increasingly unstable and may become unrecoverable from a stall or spin. Overloaded aircraft have reduced climb performance, higher stall speeds, and longer takeoff and landing distances. Many fatal GA accidents involve improper loading.
What is the CG envelope?
The CG envelope is the range of acceptable center-of-gravity positions at various gross weights, shown in the aircraft's POH/AFM. It defines forward and aft CG limits that change with weight. For a Cessna 172, typical CG limits are 35-47 inches aft of the datum at max gross weight. The envelope is depicted as a graph — your calculated weight and CG point must fall within the shaded area. Always use your specific aircraft's POH data, as limits vary even between models of the same aircraft.
How much does aviation fuel weigh?
100LL avgas weighs 6.0 pounds per gallon. Jet-A fuel weighs 6.7-6.8 pounds per gallon. These weights are at standard temperature — fuel is slightly lighter when hot and heavier when cold, but the standard values are used for weight and balance calculations. For a Cessna 172 with 56 gallons of fuel capacity, full fuel weighs 336 pounds — a significant portion of the 878-pound useful load.
What if my aircraft is over max gross weight?
If your weight and balance calculation shows you are over max gross weight, you must reduce the load before flying. Options include: reduce fuel (calculate minimum needed for the trip plus reserves), leave passengers behind, remove baggage, or split the trip into two legs with fewer passengers per leg. Never fly overloaded — insurance may not cover accidents in an overloaded aircraft, and you violate FAR 91.9. Many pilots are tempted to fly slightly over gross, but performance margins disappear quickly, especially on hot days or at high-altitude airports.