Aircraft Weight and Balance: How to Calculate It, CG Limits, and Why It Matters

Nathan Hodell
Aug 27, 2025
10 min read

Updated: May 3

Weight and balance is one of the most consequential calculations every pilot makes before every flight — and one of the most commonly half-done. Pilots glance at total weight, see it under maximum gross, and call it good. But the real risk isn't usually being a few pounds too heavy — it's having the center of gravity outside the approved envelope, which can affect everything from takeoff distance to spin recovery to whether the airplane is controllable at all.

This post covers weight and balance in practical depth: what the numbers mean, how to calculate moment and CG step-by-step, the standard weight assumptions, how fuel burn shifts the CG in flight, the effects of forward and aft CG on actual handling, and the regulations that require this calculation.

Study this full length lesson (video, podcast, flashcards, and quiz) here: Full Length Lesson >

The Vocabulary: Datum, Arm, Moment, CG

Weight and balance calculations use specific terminology. Knowing the definitions makes the math work:

Datum: The reference point from which all distances are measured. Established by the manufacturer. Could be the firewall, the leading edge of the wing, or some arbitrary point ahead of the aircraft. The datum is where "zero" is on the measuring stick.
Arm: The horizontal distance from the datum to a specific weight or point. Measured in inches. Forward of the datum = negative arm; aft of the datum = positive arm (most aircraft).
Moment: Weight multiplied by arm. This is the rotational force a weight exerts around the datum. Measured in pound-inches (or foot-pounds depending on aircraft).
Center of Gravity (CG): The point where the aircraft would balance if suspended. Calculated as total moment divided by total weight. Measured in inches from the datum.
Empty Weight: The aircraft as delivered, plus any added equipment, plus oil, plus unusable fuel. Listed in the POH.
Useful Load: Maximum gross weight minus empty weight. The maximum weight of fuel, passengers, and cargo you can add.
Maximum Gross Weight (MTOW): The maximum weight at which the aircraft is certified to take off.
Maximum Landing Weight: Sometimes lower than max takeoff weight (especially in larger aircraft); the maximum weight for landing.
Maximum Zero Fuel Weight (MZFW): Used in some aircraft; maximum weight without fuel.

The Basic Calculation: Moment = Weight × Arm

Here's the fundamental principle. Each weight in the airplane is at a specific arm (distance from datum). The moment of each weight is its weight multiplied by its arm.

Example calculation:

A pilot weighing 180 pounds sits in a seat that is 85 inches aft of the datum.

Moment = Weight × Arm Moment = 180 × 85 = 15,300 pound-inches

The pilot's moment is 15,300 pound-inches. This is the rotational tendency the pilot exerts around the datum.

The CG calculation:

Total CG = Total Moment ÷ Total Weight

Where:

Total Moment = sum of all individual moments
Total Weight = sum of all individual weights

If you know the total moment and total weight, you can calculate where the CG is located (in inches from datum).

The Standard Calculation Worksheet

Most pilots do weight and balance using a worksheet (paper or app). Here's the typical format:

Item	Weight (lbs)	Arm (in)	Moment (lb-in)
Empty weight	1,500	38	57,000
Pilot	180	85	15,300
Front passenger	160	85	13,600
Back passenger	150	120	18,000
Fuel (40 gal)	240	48	11,520
Baggage	50	140	7,000
Total	2,280	—	122,420

CG = 122,420 ÷ 2,280 = 53.7 inches aft of datum

Compare 53.7 inches to the approved CG range from the POH (e.g., 47.5 to 56.0 inches at this weight). 53.7 is within the range, so this loading is legal.

Verification check:

Calculate one item to verify your math:

Pilot: 180 × 85 = 15,300 ✓ (matches the worksheet)

This confirms the calculation method.

Standard Weight Assumptions

Some weights are standardized for calculation purposes:

Fuel:

100LL aviation gasoline: 6 pounds per gallon
Jet A: 6.7 pounds per gallon (Jet A is denser)
Diesel: similar to Jet A

Oil:

Aviation oil: 7.5 pounds per gallon (or 1.875 pounds per quart)

Passenger weight (FAA standard):

Adult average: 190 pounds (with 16 pounds of carry-on)
Some operators use 200 pounds for safety margin
Always use actual weight when known
Standard weights are estimates only — scale weights are more accurate

For pilots:

Always use actual weights when possible
Estimate generously — better safe than sorry
For training aircraft, ask your students for their actual weight (they may need encouragement to be accurate)

Reading the POH Loading Charts

Every aircraft's POH includes:

Empty Weight & CG:

Listed in the most recent weight & balance amendment
Updates required after equipment changes (avionics, paint, etc.)
Verify the empty weight is current before each flight

Loading Stations:

Each seat, fuel tank, and baggage compartment has a specific arm
Listed in the loading section
Some aircraft have multiple seat positions (forward/aft)

Loading Envelope (Graph):

Most POHs include a CG envelope graph
X-axis: Moment (in pound-inches/100 or pound-inches/1000)
Y-axis: Weight (in pounds)
Plotted point on the graph must be within the envelope

Maximum Limits:

Maximum gross weight
Maximum baggage weight
Maximum fuel weight (sometimes limited below tank capacity)
Forward and aft CG limits at various weights

Forward CG Effects: Stability and Performance

A forward CG (CG closer to the nose, toward the forward limit) has specific effects on aircraft behavior:

Increased Static Stability:

The aircraft is more stable in pitch
Less prone to pitch upsets in turbulence
More forgiving for new pilots
Trim required to maintain level flight increases

Reduced Performance:

The horizontal stabilizer must produce more downward force
More downforce = more induced drag at the tail
Higher cruise drag
Slightly slower cruise speeds
Reduced fuel efficiency (typically 1-3% at extreme forward CG)

Higher Stall Speed:

More tail downforce required means the wing must produce more lift
More lift means higher angle of attack at any given airspeed
The aircraft stalls at a higher airspeed

Increased Takeoff Distance:

More elevator input required to lift the nose
The aircraft accelerates farther before rotation
Climb rate is reduced at all altitudes
Critical at high-density-altitude airports

Recovery Characteristics:

Stalls are more pronounced and forward CG provides more nose-down tendency for recovery
Spin recovery is positive — the aircraft naturally tends to recover

Aft CG Effects: Performance and Risk

An aft CG (closer to the tail, toward the aft limit) has the opposite effects:

Reduced Static Stability:

The aircraft is less stable in pitch
More sensitive to control inputs
More prone to pitch upsets
Requires more pilot attention

Improved Performance:

Less tail downforce required
Lower induced drag
Faster cruise speeds (typically 1-3% improvement)
Better fuel efficiency
Some aerobatic aircraft are designed with intentionally aft CG for performance

Lower Stall Speed:

Less tail downforce means the wing produces less total lift
Lower angle of attack at any given airspeed
Stall occurs at lower airspeed
Can affect approach speed calculations

Reduced Takeoff Distance:

Less elevator input required
Earlier rotation
Better climb performance
Better short-field takeoff performance

Recovery Risks:

Stalls may not have a clear nose-drop
Aircraft may not recover from stalls naturally
Spin recovery becomes problematic — the aircraft may flatten in a spin
Beyond the aft limit: Spin recovery may be impossible

The Critical CG Range

Aft CG beyond the approved limit creates a particularly dangerous condition called a flat spin — a spin where the aircraft is rotating around its vertical axis with little nose-down attitude. The center of gravity is so far aft that the elevator can no longer push the tail up to break the stall.

Pilots have died from CG out of limits aft.

The limits exist because the aircraft has been certified to recover within them. Beyond those limits, the certification doesn't apply, and recovery may not be possible regardless of pilot skill.

This is why aft CG is more dangerous than forward CG:

Forward CG affects performance but maintains safety margins
Aft CG affects performance favorably but reduces safety margins
The aircraft's worst-case scenarios (stalls, spins) get progressively more dangerous as CG moves aft

In-Flight CG Shifts: The Fuel Burn Issue

Most aircraft fuel tanks are not at the same arm as the CG. As fuel burns off, the CG shifts.

Common scenarios:

Wing tanks at the same arm as CG:

Fuel burn doesn't significantly shift CG
Easy to calculate

Wing tanks aft of CG:

As fuel burns, CG moves forward
Important if loaded forward — could exceed forward CG limit at low fuel
Common in some Piper aircraft

Wing tanks forward of CG:

As fuel burns, CG moves aft
Important if loaded aft — could exceed aft CG limit at low fuel
Some aircraft like the Cessna 210 and Beechcraft Bonanza require attention

Multi-engine aircraft:

Fuel in tip tanks can shift CG significantly
Asymmetric fuel burn can cause CG shift
Cross-feed procedures help maintain balance

Calculating in-flight CG: You should calculate weight and balance for both takeoff (with full fuel) and landing (with anticipated fuel remaining). If both are within limits, the in-flight CG should remain within limits during the flight (assuming standard fuel burn from the planned tanks).

The dangerous scenario: A pilot loads the aircraft within forward CG limit at takeoff, plans a long flight, and during the flight burns fuel from a tank forward of the CG. By landing, the CG is well within forward CG limit (everything below the takeoff CG limit is within the takeoff limit), but the original loading was risky if any deviation occurred.

The reverse — loading at the aft limit — is more dangerous. If you load at the aft limit and burn fuel from a tank forward of the CG, the CG shifts further aft during flight. You may exceed the aft limit before landing.

Pre-flight calculation should account for:

Takeoff weight and CG
Landing weight and CG (with fuel burned)
The most restrictive condition during the flight

Regulatory Requirements: 14 CFR Part 91

The regulations require specific weight and balance compliance:

14 CFR 91.9 — Operating limitations

The pilot in command must have access to the POH
Must comply with operating limitations (including weight and CG)

14 CFR 91.103 — Preflight action

Pilot in command must determine the aircraft is loaded within limits
Calculations are part of preflight action

14 CFR 91.605 — Transport category aircraft

Specific weight and balance requirements for larger aircraft
Most GA pilots not affected; relevant for charter/airline operations

Practical legal effect:

Operating outside CG envelope is a regulatory violation
Could result in certificate action if discovered
More importantly: it's dangerous to safety
The legal consequences are minor compared to the safety consequences

Practical Loading Strategies

Smart loading:

Heavier passengers in the front seats (typically forward of CG)
Lighter passengers and baggage in the rear (typically aft of CG)
Distribute weight evenly between seats when possible
Use baggage compartment limits — don't exceed maximum baggage weight
For some aircraft, use forward baggage compartment to keep CG forward

Aircraft-specific considerations:

Cessna 172:

Standard configuration is generally forgiving
4 adults plus full fuel and baggage often exceeds gross weight or CG
Many flight schools restrict to 3 adults in 172

Cessna 182:

Larger but baggage compartment can be problematic
Heavy baggage with full back seat can exceed aft CG limit

Piper PA-28 (Cherokee/Warrior/Archer):

Generally forgiving CG-wise
Watch maximum gross weight with 4 adults

Beechcraft Bonanza:

Particularly sensitive to aft CG
Baggage compartment and rear seats critical
Always run the calculation

Mooney M20 series:

Long, narrow CG envelope
Easy to load aft of limit with rear passengers
Particular care needed

Common Mistakes Pilots Make

1. "It looks fine" without calculating: Visual estimation is unreliable. The math takes 5 minutes and could save your life.

2. Using "average passenger weight" without checking: Passenger weights vary dramatically. Use actual weights when known.

3. Not accounting for fuel weight changes: Calculate landing CG, not just takeoff CG.

4. Ignoring baggage compartment limits: The maximum baggage weight is a structural limit, not a weight-and-balance limit. Exceeding it can damage the aircraft.

5. Trusting outdated empty weights: After avionics installation, paint, or equipment changes, the empty weight changes. Verify the most current weight and balance.

6. Calculating only at takeoff: For long flights, calculate the most restrictive condition. CG shifts during flight matter.

7. Standard passenger weights for unusual situations: For elderly passengers, athletic teams, or other groups outside "average," use actual weights.

8. Confidence over calculation: "I always fly this loading" doesn't substitute for actual calculation when conditions or passengers change.

Modern Tools for Weight & Balance

Paper calculation: Traditional method using worksheets and calculator. Reliable, simple, no battery needed.

Spreadsheets: Custom Excel sheets for specific aircraft. Useful for repetitive calculations.

EFB Apps:

ForeFlight, Garmin Pilot, FltPlan Go all have weight & balance modules
Pre-loaded with common aircraft data
Accept user-defined aircraft profiles
Save loading scenarios for repeated use
Display the CG envelope graphically

Aircraft-Specific Apps: Some manufacturers and flight schools have proprietary weight & balance tools.

Advantage of digital tools:

Consistent calculation method
Visual envelope display
Saved scenarios for typical flights
Easy to recalculate with weight changes

Best practice: Even with digital tools, understand the underlying calculation. If your battery dies or app crashes, you should be able to do the math by hand.

On the Written Test and Checkride

Weight and balance appears consistently on tests and oral exams. The most commonly tested topics:

Definitions (datum, arm, moment, CG)
Calculation methodology (Moment = Weight × Arm; CG = Total Moment ÷ Total Weight)
Effects of forward and aft CG on stability and performance
In-flight CG shift from fuel burn
Regulatory requirements (FAR 91.9, 91.103)
Standard fuel weights (6 lb/gal AvGas, 6.7 lb/gal Jet A)

The CFI checkride and Commercial checkride often include practical weight and balance problems where you calculate loading scenarios. Practice the math.

Quick Reference

Key formulas:

Moment = Weight × Arm
CG = Total Moment ÷ Total Weight

Standard weights:

100LL AvGas: 6 lb/gal
Jet A: 6.7 lb/gal
Aviation oil: 7.5 lb/gal (1.875 lb/qt)
FAA standard adult: 190 lb (older standard 170 lb still used in some references)

CG Effects:

Forward CG	Aft CG
More stable	Less stable
Higher stall speed	Lower stall speed
More takeoff distance	Less takeoff distance
Worse cruise efficiency	Better cruise efficiency
Better recovery from stalls/spins	Worse recovery
Generally safer	More dangerous near limit

Pre-flight checklist:

Verify current empty weight from POH/W&B
Determine actual weights of pilots/passengers/baggage/fuel
Calculate moment for each item (weight × arm)
Sum total weight and total moment
Calculate CG (total moment ÷ total weight)
Verify CG is within approved envelope
Verify total weight does not exceed maximum gross
Check landing CG (with fuel burn) is also within limits

Key regulations:

FAR 91.9 — Operating limitations (compliance with W&B)
FAR 91.103 — Preflight action (calculation required)

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Author: Nathan Hodell

CFI, CFII, MEI, ATP, Creator and CEO

Nathan is an aviation enthusiast with thousands of hours of flying and dual instruction over the past 15+ years. Through his aviation career he has been able to earn his ATP, fly as an airline pilot, own/operate flight schools, and create and host wifiCFI.