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    Weight & Balance Calculator

    Add each weight and its arm to get the total weight and centre of gravity, then check them against your aircraft's limits.

    Weights in
    Arms in

    Use the units in your aircraft's weight and balance report. Switching converts the numbers you've already entered.

    StationWeight (lb)Arm (in)MomentRemove
    —
    —
    —
    —
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    Limits from your flight manual (optional)
    lb
    in
    in

    Many aircraft have a forward limit that changes with weight. Use the limit for your weight from the CG envelope chart.

    ResultUpdates as you type—Total weight—Centre of gravity—Total moment

    How your centre of gravity is worked out

    Moment = weight × arm. CG = total moment ÷ total weight.

    1. 1

      Weight × arm

      1,500 × 38.5
      = 57,750
      + 4 more rows

    2. 2

      Add the weights

      1,500 + 340 + 170 + 40 + 240
      = 2,290 lb

    3. 3

      Add the moments

      57,750 + 12,580 + 12,410 + 3,800 + 11,520
      = 98,060 lb·in

    4. 4

      Divide for the CG

      98,060 ÷ 2,290
      = 42.82 in
      inside 35–47.3 in

    Read more: the formula, a worked example and why it matters

    Every item on board has a weight and an arm, which is its distance from a reference point called the datum. Weight times arm gives the moment. Add up all the weights and all the moments, and divide the total moment by the total weight. That gives the centre of gravity (CG), measured from the same datum.

    moment = weight × arm
    CG = total moment ÷ total weight

    Worked example

    The default figures are 1,500 lb at 38.5 in, 340 lb at 37 in, 170 lb at 73 in, 40 lb at 95 in and 240 lb of fuel at 48 in. The total weight is 2,290 lb and the total moment is 98,060 lb·in, so the CG is 98,060 ÷ 2,290 = 42.8 in aft of the datum, inside the 35–47.3 in range.

    Why it matters

    A CG too far forward makes the aircraft nose-heavy and hard to rotate and flare. A CG too far aft makes it unstable and can make stall recovery impossible. Check the take-off and landing conditions, because burning fuel moves the CG.

    Fuel weights

    Avgas weighs about 6 lb per US gallon (0.72 kg per litre), and jet fuel about 6.7 lb per US gallon (0.80 kg per litre). The jet fuel converter handles exact densities.

    The default numbers are illustrative only and do not belong to any real aircraft. Always use the weights, arms and limits from your aircraft's approved flight manual and current weight and balance report.