Aircraft Weight and Balance Calculator: CG Envelope for US GA Pilots

What Weight and Balance Means for US GA Pilots Before Every Flight

It was a warm Saturday at KVNY Van Nuys Airport. A Cessna 172 carried a 240-pound pilot, two 200-pound adults in the rear seat, full baggage, and full fuel. The total loaded weight was 2,744 pounds. Maximum gross is 2,550 pounds. The aircraft was 194 pounds over gross before it ever reached the runway. This scenario plays out every weekend at airports across the country, and most pilots involved genuinely believe they are within limits because they never ran the actual numbers.

Weight and balance is two separate checks that both must pass before any flight. The weight check confirms the aircraft does not exceed its maximum certificated gross weight. The balance check confirms the center of gravity (CG) falls within the forward and aft limits published in the Pilot’s Operating Handbook. Exceed either limit and the aircraft is not airworthy. 14 CFR 91.9 prohibits flight above certificated weight limits, and the CG limits are part of the aircraft’s type certificate.

Why Both Conditions Must Be Checked Separately

An aircraft can be within gross weight but have an out-of-limits CG. A C172 with three 150-pound passengers, all in the rear two seats, no front passenger, and baggage piled in the aft compartment will be well under gross weight but potentially with an extremely aft CG. An aft CG makes the aircraft pitch-sensitive and can reduce or eliminate the nose-down pitch authority needed for stall recovery. Conversely, a solo pilot in a heavily loaded aircraft with full forward-only ballast can be under gross weight but with the CG forward of the forward limit, making it difficult to raise the nose during rotation and landing flare.

How This Calculator Differs from Paper Methods

Traditional weight and balance uses a paper worksheet, a moment table from the POH, and a CG envelope chart. You calculate each station’s moment, sum them, find the CG, and plot it on the envelope graph. This calculator automates all of that and adds two features the paper method lacks: it plots both the takeoff CG and the landing CG (after fuel burn) on the same envelope chart, and it shows you the useful load remaining after your current loading. Both are valuable for planning that goes beyond a simple go/no-go check.

How This Aircraft W&B Calculator Works: Moment, CG, and Envelope Check

The calculator uses the standard aviation weight and balance formula applied to each loading station in sequence. Select your aircraft to pre-populate the station arm values. Override the empty weight and empty arm with the actual values from your aircraft’s current weight and balance record. Then enter the weight (in pounds) at each occupied station and the fuel in gallons at both takeoff and landing.

The Moment Calculation

For each station:

1. Moment (in-lbs) = Station Weight (lbs) × Station Arm (in)
2. Add all moments including the empty aircraft moment (empty weight × empty arm)
3. Add all weights
4. CG (in) = Total Moment ÷ Total Weight

The calculator also shows the moment divided by 1,000, which is how many Cessna and Piper POHs present the data in their moment tables. Using moment/1000 keeps the numbers in a manageable range: a Cessna 172 at 2,400 lbs with CG at 39 inches has a moment of 93,600 inch-pounds, which becomes 93.6 in the moment/1000 column. Both express the same thing.

The CG Envelope Check

After calculating the takeoff CG (with full planned fuel) and the landing CG (with the landing fuel load), the calculator checks each against the aircraft’s forward and aft limits at the corresponding weight. For aircraft with a trapezoidal envelope (where the limits change with weight, which is common), the limits are interpolated at the actual takeoff and landing weights. The results are displayed as IN LIMITS (green) or OUT OF LIMITS (red) for both conditions, and both points are plotted on the envelope chart simultaneously.

Understanding the CG Envelope: Forward and Aft Limits in US GA Aircraft

The CG envelope is a chart published in the POH that shows the allowable CG range (horizontal axis) at every weight from minimum to maximum gross (vertical axis). The shape of the envelope varies by aircraft type. Understanding the shape tells you something about the aircraft’s design and typical loading challenges.

Rectangular Envelope (Cessna 172)

The Cessna 172 has one of the simplest envelopes in US general aviation: the forward and aft CG limits are essentially constant across all weights from minimum flight weight to max gross. This makes the C172 forgiving from a loading standpoint: the limits do not tighten as you add weight. The forward limit is approximately 35.0 inches and the aft limit is approximately 47.3 inches, a 12-inch range. The most common loading error in a C172 is carrying three or four adult passengers plus heavy baggage, which pushes the CG aft, combined with low fuel (forward of the CG) which makes the aft shift worse as fuel burns.

Trapezoidal Envelope (Cessna 182, most taildraggers)

The Cessna 182 and many other aircraft have a trapezoidal envelope where the aft CG limit moves aft as weight increases. This seems counterintuitive but is an aerodynamic characteristic: at lighter weights the aircraft is more sensitive and needs tighter limits, while at heavier weights the aircraft is naturally more stable. The practical implication is that you should always check both the light-weight and heavy-weight limits, since the binding constraint shifts depending on your loading.

Why Forward CG Warnings Are Also Critical

Many pilots focus on aft CG problems because they are more inherently dangerous. But forward CG should not be dismissed. A Cessna 172 with a solo 250-pound pilot, full fuel, and maximum baggage all located forward of the datum will have a CG very near the forward limit. If the elevator authority is reduced by wear in the control system or restricted elevator travel, a forward CG can prevent full-flap landing flare and result in a hard touchdown. Always check both limits.

Three Real Weight and Balance Scenarios from US GA Flight Planning

Expert Tips for Weight and Balance Loading at US Airports and FBOs

Always Get Your Aircraft’s Actual Empty Weight and Arm

The empty weight and arm in the POH from the manufacturer are the values at the time of delivery. Every aircraft since delivery has had equipment added, removed, or modified. Every repair involves some weight change. Your aircraft’s current empty weight and arm are in the weight and balance record in the maintenance logbooks, not in the original POH tables. The difference between the POH value and the current actual value can be 50 to 150 lbs for a 20-year-old GA aircraft. Always find and use the most recent W&B record entry.

Use Actual Passenger Weights, Not Standard Weights

The FAA allows airlines and charter operators to use standard passenger weights under specific conditions, but the FAA strongly recommends that GA pilots use actual weights. A pilot who estimates 170 lbs for each of three adult male passengers may be off by 60 to 90 total pounds if those passengers are each 200 lbs. On a hot day near gross weight, that error eliminates your performance margin. Ask passengers for their weights or keep a bathroom scale in your car at the airport. Most passengers are not offended if you explain it is a safety requirement.

Check Weight AND Balance: Do Not Stop at One

Many pilots check only whether total weight is under gross and stop there. Weight and balance is two separate calculations, and both must pass independently. A light solo pilot with heavy baggage all in the aft compartment can be well under gross weight but with an aft CG outside limits. A pilot who removes fuel to get under gross weight must verify the CG shifted in the right direction, because removing fuel from tanks that are aft of the CG shifts the CG forward, while removing fuel from forward tanks makes the CG go aft.

Check the Landing Condition When Fuel Burns to Known Locations

For flights longer than an hour, fuel burn moves the CG. Use this calculator to enter the planned fuel load at takeoff and at landing and verify both conditions are in limits. This is especially important for aircraft where the fuel arm is significantly different from the current CG, such as high-wing aircraft where the fuel is above the CG, or rear-fuselage-tank aircraft where the fuel is far aft. A loading that is fine at takeoff can move outside limits on a long flight.

Quick Reference: Weight and CG Limits for Common US Training Aircraft

The values below are general reference data for representative aircraft configurations. Your specific aircraft’s limits may differ due to model year, options, and STC modifications. Always use your aircraft’s type certificate data sheet and individual weight and balance record. Source: FAA Type Certificate Data Sheets (FAA.gov).

16 FAQs About Aircraft Weight and Balance, CG, and Load Limits

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