Educational calculators only. Not for operational flight planning.

Lift Force Calculator

The lift equation ties together four things: how dense the air is, how fast the wing moves through it, how big the wing is and how effectively it turns airflow into lift. This calculator multiplies them out and gives the lift force in newtons, pounds-force and kilograms-force, along with the dynamic pressure.

It is most useful for seeing proportions. Lift grows with the square of speed, so doubling the airspeed quadruples it, and it falls in step with density as altitude or temperature rises. In steady level flight lift equals weight, which is why a wing in thin air has to fly faster or at a higher lift coefficient.

Inputs

1.225 kg/m³ at sea level in the standard atmosphere.

Results

Enter your values and select Calculate.

Educational use only. Results are not certified for operational flight planning or aircraft performance decisions. Always use approved aircraft documentation and official aviation information before flight.

How to use this calculator

  1. Enter Air density in kg/m³ or slug/ft³.
  2. Enter True airspeed and choose its unit.
  3. Enter Wing area in m² or ft².
  4. Enter Lift coefficient (CL).

Standard sea-level density is 1.225 kg/m³; for other conditions the air density calculator gives a value from pressure and temperature. The speed has to be true airspeed because it is paired with the actual density. The lift coefficient is not a fixed property of an aircraft. It changes with angle of attack, flap setting and Mach number, so it has to come from data for the actual wing in the condition you are studying. The calculator accepts any value from 0 to 10 and cannot tell you whether the one you typed is realistic.

Formula

q = ½ × ρ × V²

L = q × S × CL

What the variables mean

L
lift force
q
dynamic pressure
ρ
air density
V
true airspeed in m/s
S
reference wing area
CL
lift coefficient, from wind-tunnel or flight-test data for the wing and angle of attack

Worked example

These example values are illustrative round numbers, not data for any particular aircraft. Select "Fill in the example" in the calculator to load them.

Inputs

  • Air density: 1.225 kg/m³
  • True airspeed: 100 kt
  • Wing area: 16 m²
  • Lift coefficient (CL): 0.5

Working

  1. V = 51.44 m/s, ρ = 1.2250 kg/m³, S = 16.00 m².
  2. q = ½ × 1.2250 × 51.44² = 1,621.0 Pa.
  3. L = 1,621.0 × 16.00 × 0.500 = 12,968 N.

Result

  • Lift: 12,968 N (2,915 lbf · 1,322 kgf)
  • Dynamic pressure (q): 1,621.0 Pa (33.86 lb/ft²)
  • Lift per unit area: 810.5 N/m²

Reading the result

Lift is shown in newtons with lbf and kgf beside it. Dynamic pressure (q), in pascals and lb/ft², is the ½ρV² part of the equation and depends only on the air and the speed, not on the wing. Lift per unit area is q multiplied by the coefficient; in steady level flight it equals the wing loading expressed as a pressure. For illustration, 1.225 kg/m³, 100 kt, 16 m² and a coefficient of 0.5 give 12,968 N of lift at a dynamic pressure of 1,621.0 Pa.

Assumptions and limitations

  • One lift coefficient represents the whole wing, with no variation along the span.
  • The flow is steady, with constant density and speed; gusts and maneuvers are not represented.
  • Compressibility is not calculated separately, so any Mach effect has to be inside the coefficient already.
  • The stall is not modeled: a coefficient higher than the wing can reach still produces a number, but not one that could occur.
  • The wing area is assumed to be the reference area the coefficient was defined against.
  • Only zero or positive coefficients are accepted, so negative lift cannot be explored.

Common mistakes

  • Pairing indicated airspeed with the actual density at altitude, or true airspeed with sea-level density.
  • Expecting lift to rise in proportion to speed when it follows speed squared.
  • Putting knots straight into a hand calculation that needs meters per second.
  • Treating a lift coefficient as a constant for an aircraft when it changes with angle of attack and flap setting.
  • Taking a coefficient defined on one reference area and multiplying by a different area.
  • Comparing lift in newtons with a mass in kilograms without multiplying the mass by 9.80665.

References

  1. NASA Glenn Research Center, The Lift Equation.
  2. NASA Glenn Research Center, Beginner's Guide to Aeronautics.
  3. Federal Aviation Administration, Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25).

These public sources explain the formulas and definitions used here. Citing them does not mean they have reviewed, endorsed or certified AviationCalc.

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