Weight And Balance Moment
Calculator
Results
- Moment (lb·in)
- 106,200
- Moment index (moment ÷ 1000)
- 106.2
Aviation and marine results
| Moment (lb·in) | 106,200 |
| Moment index (moment ÷ 1000) | 106.2 |
formula-map diagram
- Moment (lb·in)
- 106,200
- Moment index (moment ÷ 1000)
- 106.2
Aviation and marine relationship
Formula
Moment = weight × arm= 106200
Note
This is a simplified model: it applies a standard navigation, performance or seamanship formula to the numbers you entered. True airspeed and density altitude use the ISA troposphere model for dry air and ignore humidity, compressibility and instrument or position error, so they are not a substitute for your aircraft's flight manual or an air data computer. Wind, climb, descent and fuel figures assume a steady wind and a constant speed and fuel flow for the whole leg; they ignore manoeuvring, holding, taxi and start-up fuel, terrain, turbulence and air traffic control routing. Takeoff distance scales an entered sea level figure by a rule-of-thumb percentage per 1000 ft of density altitude and is not a certified performance chart. Weight and balance results depend entirely on the arms and weights you enter and must be checked against the approved loading envelope. Hull speed is the classic 1.34 × √LWL displacement estimate, boat fuel burn is a horsepower-based approximation, anchor scope is a rule of thumb, and the rule of twelfths is a linear approximation of a sinusoidal tide that does not hold in all locations. Always use official charts, tide tables, the aircraft or vessel manuals and current weather, and treat these numbers as planning estimates only.
More in Aviation and marine
See all →Frequently asked questions
What is a 'moment' in weight and balance calculations?+
A moment is the turning effect a weight has around a reference point (the datum), calculated as weight multiplied by its arm (distance from the datum). Moments from all items — fuel, passengers, baggage, the empty aircraft — are summed to find where the total weight effectively acts.
How is the arm different from the moment?+
The arm is simply the distance from the reference datum to where a weight is located, usually measured in inches or centimeters. The moment combines that distance with the actual weight at that location, so two items with the same arm but different weights produce different moments.
Why can't you just look at total weight to know if a load is safe?+
Two loads can have identical total weight but very different distributions — one concentrated near the tail, one balanced through the cabin — and only the moment calculation reveals where the resulting center of gravity falls. An aircraft can be under maximum weight and still be dangerously out of balance.
What's a common mistake when calculating moments by hand?+
Using inconsistent units for weight and arm (for example mixing pounds with a centimeter-based arm) or forgetting to include the basic empty weight's own moment, which already has an established arm from the aircraft's weighing report. Both errors throw off the final center of gravity result.
How does a negative arm affect the moment?+
If the datum is chosen at a point where some stations sit ahead of it, those arms are negative, and the resulting moment is also negative, effectively pulling the center of gravity forward. This is normal and expected in datum systems where the reference point is not at the extreme nose of the aircraft.