How to Calculate Weight and Balance
Weight and balance is checkride-required, FAA-required for every flight, and the cause of more accidents than most pilots realize. This guide walks through the standard CAR / FAR 91.103 calculation using a Cessna 172 as the example aircraft. The same process applies to every small piston single.
Prerequisites
- → Aircraft POH/AFM (Pilot Operating Handbook)
- → Latest weight & balance data sheet (typically updated at last annual)
- → Calculator
- → Knowledge of arms, moments, and CG basics from PPL ground school
Step-by-Step
- 1
Find the aircraft empty weight and empty CG
Listed in Section 6 of POH or aircraft equipment list. Updated whenever equipment is added/removed. Example: C172 empty weight 1,651 lb, empty CG 38.0 in.
- 2
Determine occupant and baggage weights
Weigh actual passengers if possible. Use FAA standard weights only as last resort: 190 lb adult M, 179 lb adult F, post-pandemic 195 lb avg. Baggage actual.
- 3
Calculate fuel weight
Avgas = 6.0 lb/gal. Jet A = 6.7 lb/gal. C172 with 56 gal usable fuel x 6 lb/gal = 336 lb max.
- 4
List arms (distance from datum) for each station
Pilot/copilot 37 in, rear pax 73 in, baggage 1 95 in, baggage 2 123 in. Specific to aircraft — check POH.
- 5
Calculate moments (weight x arm) for each station
Add empty aircraft moment to each new station's moment. Example: 200 lb pilot x 37 in = 7,400 lb-in.
- 6
Sum total weight and total moment
Total weight: empty + occupants + fuel + baggage. Total moment: sum of all moments including empty.
- 7
Calculate CG (total moment / total weight)
Example: total weight 2,300 lb, total moment 92,000 lb-in. CG = 92,000 / 2,300 = 40.0 in aft of datum.
- 8
Check against the CG envelope
Plot the (weight, CG) pair on the envelope chart in Section 6 POH. Must fall inside the envelope for the configuration. If outside: redistribute load (move bag forward/aft, swap pax seats, reduce fuel).
Common Mistakes
- × Using outdated empty weight from POH instead of current weighing
- × Forgetting to subtract usable vs unusable fuel
- × Missing that fuel burn shifts CG aft on most singles (unburnable forward fuel)
- × Not checking takeoff AND landing CG (heavier landing CG aft due to fuel burn)
Pro Tips
- ★ Use a digital W&B app like ForeFlight to remove arithmetic errors
- ★ Pre-load common configurations (solo, full pax, max fuel) and save
- ★ Always check the LANDING configuration too — out-of-envelope landing is the more common error
- ★ Print and keep a paper copy in the aircraft for cross-check
Conclusion
Weight and balance takes 5 minutes to compute and is non-negotiable. Many fatal accidents trace to overweight or out-of-envelope loadings. Make the calculation a checklist item before every flight, just like a fuel check.
FAQ
Do I have to do W&B for every flight?
Yes. FAR 91.103 requires the PIC to be familiar with all available information — weight and balance is part of that for every flight.
What if I'm slightly aft of the CG envelope?
Move baggage forward, swap rear pax to front, or reduce rear fuel. Never depart with knowingly out-of-envelope CG.