Wing Loading Calculator (kg/m², lb/ft² and stall speed)

Understanding the wing loading calculator — concept and principle

Wing loading is an aircraft's weight divided by its wing area. It strongly affects how fast the aircraft must fly to stay airborne, how it handles gusts and how long its take-off and landing runs are. This calculator gives wing loading in kg/m², N/m² and lb/ft², and estimates the stall speed from the maximum lift coefficient and air density.

Heavier loading per square metre means a higher stall speed.

How it is calculated

Wing loading = m ÷ S

Vstall = √(2 m g ÷ (ρ S CL,max))

m aircraft mass (kg), S wing area (m²), g = 9.80665 m/s².
CL,max is the maximum lift coefficient of the wing (higher with flaps), ρ the air density (1.225 kg/m³ at sea level in the standard atmosphere).
Stall speed is shown in m/s, km/h and knots (1 knot = 1,852 m/h).

The principle

In level flight, lift must equal weight. NASA's lift equation says lift = CL × ½ρV² × S. Each square metre of wing can only produce so much lift at a given speed, limited by CL,max. Setting lift equal to weight and solving for speed gives the slowest speed at which the wing can still support the aircraft: the stall speed. Weight per area appears directly under the square root, so a higher wing loading means a higher stall speed. Thinner air at altitude or on hot days lowers ρ and raises the true stall speed too.

Worked example

Default inputs: mass 1,100 kg, wing area 16.2 m², CL,max 1.6, ρ = 1.225 kg/m³.

Wing loading = 1,100 ÷ 16.2 = 67.9 kg/m² = 67.9 × 9.80665 = 666 N/m² = 13.91 lb/ft².
Weight = 1,100 × 9.80665 = 10,787 N.
Vstall = √(2 × 10,787 ÷ (1.225 × 16.2 × 1.6)) = √679.5 = 26.1 m/s.
In other units: 94 km/h = 51 knots.

Each point is the calculator re-run with only “Wing area (m²)” changed; the gold point is the default example. Change the inputs above and this chart follows your numbers.

Wing area (m²)	Wing loading (kg/m²)
4.05	271.6
8.1	135.8
12.2	90.5
16.2	67.9
20.2	54.3
24.3	45.3
32.4	34

How to read the result

Gliders and light trainers have low wing loadings and land slowly; airliners and fast jets have high wing loadings and need long runways and powerful flaps. High wing loading gives a smoother ride in turbulent air, while low wing loading allows slow, short-field flying. In a turn, the load factor n raises the stall speed by √n: in a 60° bank, n = 2 and stall speed rises by about 41 %.

Common mistakes

Mixing mass and weight units, for example kg with N/m².
Using the clean-wing CL,max for a landing with flaps, or the reverse.
Forgetting that stall speed rises in turns and at higher altitude (true airspeed).
Using a design CL instead of the maximum value.

Keep in mind: This is an estimate for level, unaccelerated flight. Always use the stall speeds in the aircraft's approved flight manual for operations.

Frequently asked questions

What is a typical wing loading for a light aircraft?

Many light single-engine aircraft fall roughly in the 50–90 kg/m² range.

Why do flaps lower stall speed?

They raise CL,max, so the wing makes more lift at a given speed.

Does altitude change stall speed?

The indicated stall speed stays about the same, but the true airspeed at stall rises as air density falls.

How does weight affect stall speed?

Stall speed scales with the square root of weight; 10 % more weight gives about 5 % higher stall speed.

Sources: NASA Glenn Research Center, Beginner's Guide to Aeronautics, "Lift Equation"

Checked 9 Nov 2026. NASA Glenn Research Center, Beginner’s Guide to Aeronautics, “Lift Equation” (L = C_l · ρV²/2 · A, A = wing area). Wing loading W/S is the standard definition; unit factors from the exact definitions of the pound (0.45359237 kg), foot (0.3048 m) and nautical mile (1,852 m).

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