How to Calculate Weight and Balance: A Step by Step Guide

In this article I’m going to teach you how to calculate weight and balance quickly and easily.

As a flight instructor I’ve taught this skill to many of my students. It’s an absolutely critical part of your pre-flight planning.

Learning how to calculate aircraft weight and balance is one of the most fundamental preflight skills a pilot learns. In training aircraft, it’s a basic and easy calculation that will eventually become second nature.

As you move into larger aircraft the weight and balance can become more challenging. Your goal should be to practice it until it becomes ingrained, and having a calculated weight balance for every flight should be non-negotiable.

Luckily, weight and balance don’t require crazy math skills or hours of hard work. Instead, it’s a simple calculation that you will learn to knock out in a few minutes.

Here’s a step-by-step guide to making it happen in any aircraft. There is also new technology, like ForeFlight, that makes these calculations a breeze.  

Why Calculate Weight and Balance?

It’s easy to say you must do your aircraft weight and balance before every flight because your flight instructor says so, but why do they say so? 

Each weight and balance problem component is a critical limitation on the aircraft. Few performance or safety items are more important than knowing that your flight is within limits.

The regulations do not explicitly require you to calculate your weight and balance before every flight, however it is implied. The regulations stipulate that you calculate your takeoff and landing distances and operate the airplane according to the AFM.

If you don’t know your weight and balance, you can’t comply with that regulation. (14 CFR Part 91.9)

Weight

We all know that airplanes are only built to support so much weight. Whatever limitations are printed in Chapter 2 of your POH/AFM will be your guide. The most important number is the maximum takeoff weight. 

Operating beyond maximum weight puts you into the realm of the test pilot. Here are just a few of the negative flight characteristics you might expect.

• Higher takeoff speeds with longer takeoff rolls
• Longer landing rolls
• Reduced performance, including slower cruise speeds and slow climbs
• Higher stall speeds 
• Limits on landing gear and brakes exceeded
• More load put on the structure of the aircraft then it was designed for 

Balance

Finding whether or not your airplane is in balance is all about finding the loaded airplane Center of Gravity or CG. Once you have this, you can compare it to the charts or tables the manufacturer gives you to ensure that it is within acceptable limits.

The CG cannot be too far forward nor too far back. Either situation will make the airplane dangerous and potentially unstable.

A CG located forward of the forward limit will cause the airplane to have a nose-down tendency. If the loading is severe enough, the elevator travel may not produce enough force to allow the airplane to flare or rotate.

The nose-down tendency will increase the airplane’s stall speed and make cruise flight much slower.

If the CG is located too far aft, the airplane will have a nose-up tendency. This typically is the most dangerous situation. The aircraft will have a noticeably higher cruise speed, but the aircraft will be much less stable. 

Should the airplane begin pitching up and slowing, as in a stall scenario, it may be impossible for the pilot to lower the nose, reduce the angle of attack, and recover. 

A rearward out-of-limits CG is associated with unrecoverable stalls and spins.

Weight and Balance Terms

Standard empty weight — The weight of the airframe, engines, and permanently installed fixtures and fluids (including unusable fuel and full engine oil)

Basic empty weight — Standard empty weight plus any accessories your airplane might have added

Licensed empty weight — An older term than “standard empty weight,” which does not include engine oil

Maximum ramp weight — Total loaded aircraft weight only published for some airplanes. This will be a few pounds heavier than maximum takeoff weight because it assumes you will burn some for taxi and run-up.

Maximum takeoff weight — Maximum weight you can take off with.

Maximum landing weight — Maximum weight you can land with. This is not always published, or it may be published as equal to takeoff weight. Larger aircraft have landing weights much less than takeoff weights since they are designed to burn hundreds (or thousands) of pounds of fuel during flight.

Maximum zero fuel weight — The loaded aircraft weight with everything except fuel. Only published for some aircraft. This is a loading figure to reduce stress on the wings.

Payload — A common term for the maximum weight an airplane can carry of things that can pay the bill—passengers or cargo. 

Useful load — A common term for what an airplane can carry that the pilot loads aboard—pilot, passengers, cargo, and fuel. It is found by taking the maximum takeoff weight and subtracting out the aircraft’s basic empty weight.

Datum — A reference point chosen by the manufacturer from which all arms are measured. Where it doesn’t matter, but it is usually located at the tip of the propeller spinner or the engine firewall.

Arm — The distance measured fore or aft of the datum. Every location a pilot can load an object will have an arm distance listed in the POH/AFM. If an arm is located forward of the datum, it will be a negative number.

Station — A location in the airplane where you can load something. Examples of stations include front seats, rear seats, main baggage area, nose baggage area, fuel tanks, etc.

CG — The center of gravity measured in inches aft of the datum. The airplane will have a minimum and maximum CG location for every available weight.

Moment — A measurement of the force that an item places on the airplane. A 100-pound object will produce more force the farther away from the datum that it is located. In other words, a 100-pound bag will affect your CG location more the farther back in the airplane it is located. Moments are measured in inch-pounds.

Moment index — Moments are usually long numbers, so many POH/AFMs index them to simplify the math. This simply means they divide them by either 100 or 1,000. So 123,456.0 in-lbs becomes 1,234.56 or 123.456. 

Three Methods to Calculate Weight and Balance

It is often said that there are three methods or ways to calculate aircarft weight and balance, but that’s not entirely true. All of these “methods” are based on calculating the weight and balance with a simple math formula. 

A better way of saying it is that your POH or AFM will provide you with one or more of these three ways to do the work. You’ll either use numbers to do the math, find the numbers on a graph, or find the numbers on a table.

Calculation Method

To some extent, all weight and balance calculations come back to the mathematic formula for weight and balance. 

Weight x Arm = Moments

Figuring out the weight and balance by calculation alone simply means that you do the math for everything—all of the numbers are filled out line by line. The other methods simply make your life a little easier by giving you some of that information quickly.

Understanding the calculation method is important because it is the basis for the other methods. If you can figure out the airplane’s weight and balance this way, you can figure it out anyway.

Graph Method

If your POH or AFM includes graphs, you’ll get at least two. 

The first will show how many moments an item produces at each station. So each station of the airplane (front seats, rear seats, fuel, baggage, etc.) will have its own line on the graph. On the bottom will be weight, and on the side will be moments.

Once you have tallied each item in the airplane, simply add total weight and total moment. A second graph will show you the acceptable CG limits using these two numbers. 

Table Method

Tables are similar to graphs, only they will provide tables of numbers for every station and a similar table for the CG limits. 

Like the graph method, the only math involved should be totaling the weight and moments column. 

Tables may require you to round your numbers up a bit since each item will be listed for even-numbered weights. For example, if your front passengers weigh 345 pounds total, you might use the 350-pound line. Alternatively, you could use the provided arm and resort to the calculation method to get a more precise number.

Finding the Weight and Balance with the Calculation Method

Step 1 – Make Your Table

Weight and balance start with a blank table that you can fill out for every flight. Many schools and FBOs provide you with a planning sheet, but it’s easy to make your own. 

The first column will be “weights,” the second “arm,” and the third will be “moments.” To remind yourself, you can write the aircraft weight and balance formula at the top. 

Weight x Arm = Moments

The usual line items will be as follows. The list will depend on the available stations for loading in your aircraft. The first line will always be the empty weight of the airplane.

	Weight       x	Arm      =	Moments
Empty weight	?	?	?
Pilot + Copilot	?	?	?
Rear passengers	?	?	?
Fuel — main tanks	?	?	?
Fuel — aux tanks	?	?	?
Baggage area 1	?	?	?
Baggage area 2	?	?	?
Total	?	?	?

Step 2 – Find the Aircraft’s Empty Weight and Moment

You can’t do the paperwork until you know which airplane you’ll be flying. The only official source for the empty weight, CG, and moment of the airplane is the official record found in that particular airplane’s POH/AFM. Do not use the sample information found online or in your personal PIM. 

The official record comes from the last time a mechanic physically weighed aircraft. It should be signed by the A&P and specific to that airplane. 

From this form, you need the empty weight and the total moments. Add these to the first row of your table.

	Weight       x	Arm      =	Moments
Empty weight	2,100	78.3	164,430
Pilot + Copilot	?	?	?
Rear passengers	?	?	?
Fuel — main tanks	?	?	?
Fuel — aux tanks	?	?	?
Baggage area 1	?	?	?
Baggage area 2	?	?	?
Total	?	?	?

Step 3 – Weight Your Gear and Passengers

Fill out all of the items in the weight column. Estimates aren’t good enough in a small airplane—you should use exact numbers. Don’t be afraid to ask your passengers how much they weigh. Many FBOs have a scale you can use if they don’t know. Remember to include heavy jackets and boots if it’s wintertime!

You should know how many gallons of fuel your airplane holds, but how much does it weigh? Avgas weighs 6 pounds per gallon, so multiply the gallons by 6. (If your airplane burns Jet-A, you’ll have a table that will tell you how much it weighs at various temperatures—it’s usually a little over 7 pounds per gallon.)

Remember to include everything in the airplane that isn’t bolted down. Commonly missed items are flight bags thrown in the rear seats or spare parts, oil, and various things stored in the baggage area.

	Weight       x	Arm      =	Moments
Empty weight	2,100	78.3	164,430
Pilot + Copilot	340	?	?
Rear passengers	350	?	?
Fuel — main tanks	450	?	?
Fuel — aux tanks	0	?	?
Baggage area 1	80	?	?
Baggage area 2	0	?	?
Total	?	?	?

Step 4 – Find the Arm for Each Station

Next, you need to know the arm for each weight on your list. This comes from Chapter 6 of your POH/AFM. Fill out your table.

	Weight       x	Arm      =	Moments
Empty weight	2,100	78.3	164,430
Pilot + Copilot	340	85.0	?
Rear passengers	350	121.0	?
Fuel — main tanks	450	75.0	?
Fuel — aux tanks	0	–	?
Baggage area 1	80	150.0	?
Baggage area 2	0	–	?
Total	?	?	?

Step 5 – Find the Moment for Each Line Item

Do the multiplication for each row to solve for the moment.

	Weight       x	Arm      =	Moments
Empty weight	2,100	78.3	164,430
Pilot + Copilot	340	85.0	28,900
Rear passengers	350	121.0	42,350
Fuel — main tanks	450	75.0	33,750
Fuel — aux tanks	0	–	0
Baggage area 1	80	150.0	12,000
Baggage area 2	0	–	0
Total	?	?	?

Step 6 – Find Total Weight

Add up the weight column. Is your total weight under the maximum takeoff weight for your airplane?

If you are over maximum takeoff weight, you’ll want to double-check your numbers. You might need to leave some items (or people!) behind. Or, you could consider leaving with less fuel if it is safe to do so. 

	Weight       x	Arm      =	Moments
Empty weight	2,100	78.3	164,430
Pilot + Copilot	340	85.0	28,900
Rear passengers	350	121.0	42,350
Fuel — main tanks	450	75.0	33,750
Fuel — aux tanks	0	–	0
Baggage area 1	80	150.0	12,000
Baggage area 2	0	–	0
Total	3,320	?	?

Step 7 – Find Total Moment and CG

Your POH/AFM will provide a way to find whether or not the airplane is in balance. It will provide the answer using the total moments, total arm (CG), or both.

Add up the moment column. This will be enough if you have a chart in your POH/AFM for the loaded moments. Remember to correct it to the appropriate index that matches the information in your POH. You may have to divide by either 100 or 1,000.

	Weight       x	Arm      =	Moments
Empty weight	2,100	78.3	164,430
Pilot + Copilot	340	85.0	28,900
Rear passengers	350	121.0	42,350
Fuel — main tanks	450	75.0	33,750
Fuel — aux tanks	0	–	0
Baggage area 1	80	150.0	12,000
Baggage area 2	0	–	0
Total	3,320	?	281,430

If you need to solve for CG, take your total moment (unindexed) and divide by the total weight. A common mistake is to add up all of the arms, but this will not provide a helpful number. Instead, you need to calculate it based on the weights and forces in the airplane, which are represented by the moments and weight. 

	Weight       x	Arm      =	Moments
Empty weight	2,100	78.3	164,430
Pilot + Copilot	340	85.0	28,900
Rear passengers	350	121.0	42,350
Fuel — main tanks	450	75.0	33,750
Fuel — aux tanks	0	–	0
Baggage area 1	80	150.0	12,000
Baggage area 2	0	–	0
Total	3,320	CG = 84.8*	281,430

*CG = Moments/Weight = 281,430/3,320 = 84.8

Remember – Weight and Balance Before Every Flight

If, after all this work, you find your airplane overweight or out of CG limits, you’ll need to take action to correct it before departure. Weight issues are usually fixed by reducing the fuel load in the aircraft, while you can fix CG problems by moving the load around inside the airplane. 

Once you’re comfortable calculating the weight and balance for your routine training flights, practice a long trip with passengers and bags. You might be surprised how easy it is to overload or dangerously load a small GA airplane!

For further reading, Weight and Balance are covered in Chapter 10 of the FAA’s Pilot’s Handbook of Aeronautical Knowledge.

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