Weight Shift CG Calculator
When you relocate cargo or passengers in an aircraft, the centre of gravity moves by an amount that depends on how much weight moved, how far, and the total aircraft weight. This calculator uses the standard moment method: it finds the CG shift for relocated weight and the resulting new CG. Enter your starting CG and weight, the weight that moves, and the distance it moves. Compare the new CG against your aircraft's published limits.
Weight shift CG formula
CG shift = (weight moved * distance moved) / total weight
New CG = current CG + CG shift
A positive distance is aft (toward the tail) and a negative distance is forward. Use consistent units throughout, typically pounds and inches from the datum.
Worked example
- Total weight 2,400 lb, current CG 88.5 inches.
- Move a 120 lb bag 40 inches aft.
- CG shift = (120 * 40) / 2,400 = 2.00 inches aft.
- New CG = 88.5 + 2.00 = 90.50 inches.
Weight shift CG: frequently asked questions
How does moving weight shift the centre of gravity?
The centre of gravity shift equals the moved weight times the distance it moves, divided by the total aircraft weight. CG shift = (weight moved * distance moved) / total weight. Moving weight aft shifts the CG aft, and the larger the weight or the distance, the bigger the shift.
What is the moment method?
A moment is weight times arm (the distance from the reference datum). The centre of gravity is the total moment divided by the total weight. When you add, remove, or move weight you recompute the total moment and divide by the new total weight to find the new CG.
Does the same formula work for adding or removing weight?
Yes. For added or removed weight, new CG = (old total moment plus or minus the item moment) / (new total weight). This calculator offers a shift mode for relocating existing weight and an add or remove mode for changing the load.
Why must I keep the CG within limits?
A CG too far forward or aft affects controllability and stall behaviour and can make the aircraft unsafe or impossible to recover. The forward and aft CG limits are published in the aircraft Pilot's Operating Handbook; this tool reports the new CG so you can compare it against those limits.
Official sources
- FAA: Aircraft Weight and Balance Handbook.
- FAA: Pilot's Handbook of Aeronautical Knowledge (weight and balance).
Reviewed by the CalculatorHub team, edited by James Graham, 19 June 2026. See our methodology.