Induced Drag Calculator

Calculator Inputs

Input mode

Choose how the calculator determines CL.

Lift or weight (L)

For level flight, L is approximately weight.

Lift coefficient (CL)

Typical cruise values: 0.2 to 0.6.

Wing area (S)

Reference planform area.

Aspect ratio (AR)

AR = b^2 / S for wings.

Oswald efficiency (e)

Common range: 0.7 to 0.95.

Speed (V)

Use true airspeed for best results.

Air density (rho)

Sea-level ISA is about 1.225 kg/m3.

Display precision (decimals)

Set rounding for tables and exports.

Clear

Formula Used

Dynamic pressure

q = 0.5 * rho * V^2

rho is density, V is speed.

Lift coefficient

CL = L / (q * S)

If you input CL, L is derived.

Induced drag coefficient

CDi = CL^2 / (pi * e * AR)

e and AR capture span efficiency.

Induced drag force

Di = q * S * CDi

Force from trailing vortices.

Induced drag power

Pi = Di * V

Power needed to overcome induced drag.

Induced factor

k = 1 / (pi * e * AR)

Then CDi = k * CL^2.

How to Use This Calculator

Select an input mode: Lift/Weight or CL.
Enter wing area, aspect ratio, and efficiency factor.
Set speed and air density for the condition.
Click Calculate to view results above the form.
Use CSV or PDF export buttons to download.

Example Data Table

Case	S (m2)	AR	e	rho (kg/m3)	V (m/s)	L (N)	CL	CDi	Di (N)
Trainer	16	8	0.80	1.225	60	15000	0.4252	0.0090	317.19
Jet cruise	50	9.5	0.85	0.380	230	80000	0.1592	0.0010	502.01
Glider	14	18	0.95	1.000	40	3500	0.3125	0.0018	20.36

Examples are illustrative and assume steady conditions.

FAQs

1) What is induced drag?

Induced drag is the drag created when a wing generates lift. It comes from wingtip vortices and downwash, and it rises sharply at higher lift coefficients, especially during takeoff, climb, and slow flight.

2) Why does induced drag increase at low speed?

At lower speed, the wing must produce the same lift with a higher CL. Because CDi scales with CL squared, induced drag grows quickly when you slow down or pull more load factor.

3) What does the Oswald efficiency factor mean?

e measures how close the wing’s lift distribution is to ideal. Higher e means less induced drag for the same CL and aspect ratio. Typical values range from about 0.7 to 0.95.

4) How does aspect ratio affect induced drag?

Higher aspect ratio spreads lift over more span, weakening vortices. Since CDi is inversely proportional to AR, increasing AR reduces induced drag, which is why gliders use long, slender wings.

5) Can I use weight instead of lift?

Yes. In steady, level flight, lift is approximately equal to weight. Enter weight as L and the calculator will treat it as the lift requirement. For turns or climbs, lift can exceed weight.

6) What units should I use?

Use any provided unit set consistently: N or lbf for forces, m2 or ft2 for area, and m/s, km/h, or knots for speed. The calculator converts internally and reports outputs using your selected force unit.

7) Why is L/Di different from aircraft L/D?

This L/Di considers induced drag only. Real aircraft drag includes parasitic and profile components, so total L/D is lower. Use this value mainly to compare induced drag changes with AR, e, or CL.

8) Is this accurate for all flight regimes?

It’s a standard approximation for subsonic, attached-flow conditions. At high Mach, high angles of attack, or near stall, additional effects can dominate. Use validated aerodynamic data for critical design decisions.