This weight and balance example Cessna 172 walkthrough covers the full calculation step by step, from empty weight to final centre of gravity (CG). If you already know the theory and just want to see the numbers worked out, this article is for you.
For the formulas and definitions behind each step, see our guide on weight and balance in Excel. This article focuses only on walking through one worked example.
Before you start: about these numbers
The weight, arm and moment figures used below are example numbers, chosen to keep the maths easy to follow. They are not the real weight and balance data for any specific Cessna 172. Every aircraft has its own empty weight, arms and CG envelope, recorded in its own approved weight and balance report. Always use the numbers from your aircraft’s POH, AFM or weight and balance report, never the numbers in this example. If you are a student pilot, ask your instructor to confirm your figures.
Step 1: Start with the empty weight and moment
Every calculation starts with the aircraft’s basic empty weight and its arm, both found in the aircraft’s approved documents.
- Empty weight: 1,480 lb
- Arm: 39.0 in
- Moment: 1,480 × 39.0 = 57,720 lb-in
Step 2: Add the pilot and front passenger
- Weight: 340 lb
- Arm: 37.0 in
- Moment: 340 × 37.0 = 12,580 lb-in
Step 3: Add rear passengers
- Weight: 300 lb
- Arm: 73.0 in
- Moment: 300 × 73.0 = 21,900 lb-in
Step 4: Add fuel
Fuel is usually loaded by volume, so it needs to be converted to weight first. Avgas 100LL weighs approximately 6 lb per US gallon.
- Fuel: 38 gal × 6 lb/gal = 228 lb
- Arm: 48.0 in
- Moment: 228 × 48.0 = 10,944 lb-in
Step 5: Add baggage
- Weight: 50 lb
- Arm: 95.0 in
- Moment: 50 × 95.0 = 4,750 lb-in
Step 6: Add up the totals
| Item | Weight (lb) | Arm (in) | Moment (lb-in) |
|---|---|---|---|
| Empty aircraft | 1,480 | 39.0 | 57,720 |
| Pilot + front passenger | 340 | 37.0 | 12,580 |
| Rear passengers | 300 | 73.0 | 21,900 |
| Fuel | 228 | 48.0 | 10,944 |
| Baggage | 50 | 95.0 | 4,750 |
| Total | 2,398 | — | 107,894 |
Step 7: Calculate the CG
CG = Total moment ÷ Total weight
CG = 107,894 ÷ 2,398 = 45.0 in aft of datum
Step 8: Check the CG against the envelope
The final step is to plot this weight and CG position on the aircraft’s own CG envelope chart, from its POH or AFM. If the point falls inside the approved envelope, the loading is within limits. If it falls outside, weight has to be adjusted, for example by reducing baggage, fuel or moving passengers, and the calculation redone before flight.
Doing this without redoing the maths every time
Working through the arms and moments by hand is useful once, to understand the process. For day-to-day flying, most pilots prefer a spreadsheet that keeps the same aircraft profile saved and does the arithmetic automatically. Our Weight and Balance Spreadsheet works exactly like this example: you set up your aircraft’s real empty weight, arms and CG envelope once, then enter the weights before each flight and it calculates the total weight, moment and CG for you, with a chart to check the result at a glance.
Frequently asked questions
Are the numbers in this example accurate for my Cessna 172? No. They are example figures used to demonstrate the calculation method. Every Cessna 172 has its own empty weight, arms and CG envelope, listed in its own approved weight and balance report. Always use your aircraft’s own numbers.
What if my calculated CG falls outside the envelope? Adjust the load, for example by reducing baggage, reducing fuel, or repositioning passengers, and recalculate. Never depart with the CG outside the approved envelope.
Does this replace checking the POH? No. This example only illustrates the calculation steps. The weight, arm and CG envelope you use for an actual flight must always come from the aircraft’s own approved documentation.
