Wing Loading Calculator

The wing loading is the weight that an aircraft carries per unit area of its wing. It has a nearly decisive influence on the flight properties of an aircraft. It determines how fast an aircraft must fly to remain in the air and how tight it can turn.

This value is important whether you're designing a foam glider, tuning a training plane or assessing the performance of a commercial airliner. Enter weight and wing area to get wing loading, or enter any two of the three values and leave the third blank to calculate it.

What is wing loading?

It can be thought of as the average load applied per square meter of wing area. Heavier aircraft with shorter, wider wings have a higher wing loading and therefore need to fly faster in order to generate enough lift. If you put larger wings on the same plane, the wing loading will decrease, allowing it to fly slower while still maintaining altitude.

This compromise affects performance in opposite ways. A high wing loading increases the stall speed and lengthens the takeoff roll but also provides a smoother ride through turbulence. This is one of the reasons that commercial airliners can fly safely even in turbulent airflows.

Less weight allows tighter turns, shorter takeoff distances and gentler handling at low speeds but also increases susceptibility to turbulence. A glider is operated with a load near the lower end of the scale while a Boeing 747 would be more toward the high side.

Formula for wing loading:

The wing loading is equal to weight divided by wing area.

In this formula, WL is the wing loading, W is the total weight of the aircraft and S is the reference area of the wing. As it's an equation with three variables, the formula can be rearranged to calculate any one of the missing variables.

An example of a calculation:

Let's take the commonly used training aircraft Cessna 172 Skyhawk as an example. It weighs about 1,100 kilograms and has a wing area of 16.2 square meters.

The low wing loading is one reason the Cessna can fly at just under 90 km/h and land on short runways, which are exactly the qualities required for a training airplane.

Let's take another F-16 with a typical takeoff weight of 12,000 kilograms and a wing area of 28 square meters.

This is six times the wing loading of a Cessna. The F-16 is very stable at high speeds but has a landing speed of about 260 km/h.

Wing loading and stall speed

The most important aspect of the lift curve is that it tells you how slow an airplane can fly. At stall, lift equals weight, so the minimum flying speed comes from the lift equation:

Wing loading is the weight (W) divided by wing area (S), g is the acceleration of gravity, ρ is the Greek symbol for air density and the last term is the maximum lift coefficient that the aircraft can achieve. With the above function to estimate stall speed you can do calculations with your own values.

The important thing is that the speed only increases very slowly. If the wing loading is quadrupled, the stall speed only doubles, which is a square root relationship as defined in the above equation. This is why heavy jetliners with ten times the useful load of a light plane can still land at reasonable speeds.

kg/m² compared to N/m²

There are two common conventions that represent the same quantity in different ways. The "kilograms per square meter" version treats weight as a mass and is almost always used by pilots, aviation engineers, and modelers.

The version "Newton per square meter" considers the weight as a force and is used in formal aerodynamics since the lift equation is based on forces. To convert just multiply the mass load by 9.81. The result sheets show both values simultaneously so you don't have to do your own conversion.

Wing volume load in model aircrafts

Model aeronauts use a variant of wing loading called wing volume loading (WCL). Normal wing loading is unfair to small models; when an aircraft is scaled down, its area goes down with the square of size while its weight goes down with the cube of size. Thus small model and full-size aircraft with the same wing loading will have very different flight characteristics.

Wing cube loading solves this problem by dividing the weight by the 1.5th power of the wing area, giving a value for the weight per unit volume which is essentially density:

A happy coincidence makes this value easy to understand. When calculating with metric units (kilograms and square meters), the result is kg/m³. This value deviates by less than one percent from the values that model airplane enthusiasts have long been calculating in ounces per cubic foot. Regardless of which unit is used, the known control degrees apply.

Reference values for aircraft wing loading

These rounded values show the extent of the load range, from light sailplanes to heavy transport aircraft. With the above comparison function you can represent your own plane on the same scale.

Use of wing loading

Designers select a target wing loading in the early stages of design and use this to determine the size of the wings needed for desired cruise speed, range or takeoff distance. Pilots and engineers compare the loadings of different aircraft as a quick way to assess an aircraft's performance characteristics and limitations.

In the construction of remote-controlled models and drones this value is typically given in grams per square decimeter, which allows to predict flight properties before the model leaves the workshop. Glider designers use a low wing loading to extend the glide performance and reduce sink rate.

Wing loading recommendations:

During a flight the wing loading will decrease as fuel is consumed. Therefore, the wing loading of an aircraft fully fueled will be higher than that of the same aircraft shortly before it runs out of range. Long-haul airliners can burn thousands of kilograms of fuel, which results in a significant change to their wing loading.

When comparing aircraft it is important to use the same standard of weight for each aircraft, whether that be empty weight, maximum takeoff weight or typical operating weight. Using different standards is the most common cause of skewed comparison results.

Note that wing loading alone does not tell the whole story; the shape of the wing, its profile, aspect ratio and thrust to weight ratio affect an aircraft's actual flight performance. So two planes with the same wing loading but different geometry can perform very differently.