Pilots fly through moving air. To track a course over the ground, they point the nose slightly into the wind (the wind correction angle), and the wind also speeds up or slows down their ground speed – which sets the flight time and fuel needed.
How to use the Ground Speed Calculator
- True airspeed
- Course α
- Wind speed
- Wind direction β (from)
Results update as you type, every field has its own unit menu, and everything is calculated in your browser.
How it works
Enter the true airspeed, the course you want to fly over the ground, and the wind (the direction it blows from). Angles are true bearings in degrees.
Inputs explained
| Field | What to enter |
|---|---|
| True airspeed | Units: knots, km/h, mph, m/s |
| Course α | Units: °, rad, arcmin, arcsec, mrad |
| Wind speed | Units: knots, km/h, mph, m/s |
| Wind direction β (from) | Units: °, rad, arcmin, arcsec, mrad |
What each result means
- Wind correction angle = deg(asin([Wind speed]×sin(rad([Wind direction β (from)] – [Course α]))÷[True airspeed]))
- Heading = mod([Course α] + [Wind correction angle], 360)
- Ground speed = [True airspeed]×cos(rad([Wind correction angle])) – [Wind speed]×cos(rad([Wind direction β (from)] – [Course α]))
- Headwind component = [Wind speed]×cos(rad([Wind direction β (from)] – [Course α]))
- Crosswind component = [Wind speed]×sin(rad([Wind direction β (from)] – [Course α]))
Example values
How the main result changes when True airspeed changes and everything else stays at the example values above:
| True airspeed (knots) | Ground speed (knots) |
|---|---|
| 60 | 47.45 |
| 90 | 78.32 |
| 120 | 108.74 |
| 150 | 139 |
| 180 | 169.16 |
| 240 | 229.37 |
Formula
WCA = arcsin(V_w·sin(β − α) / TAS), heading = α + WCA
GS = TAS·cos(WCA) − V_w·cos(β − α)
Worked example
Inputs — True airspeed: 120 knots; Course α: 90 °; Wind speed: 20 knots; Wind direction β (from): 30 °.
Results — Wind correction angle = -8.3 °; Heading = 81.7 °; Ground speed = 108.74 knots; Headwind component = 10 knots; Crosswind component = -17.32 knots.
Key terms
- True airspeed
- Speed relative to the air mass.
- Ground speed
- Speed relative to the ground.
Frequently asked questions
What is the wind correction angle?
The angle between heading and course needed to cancel the crosswind drift.
Is wind direction "from" or "to"?
Aviation winds are reported as the direction they blow from.
Why is ground speed lower into a headwind?
The air mass moves backwards relative to the ground.
What if the crosswind is stronger than the airspeed?
The course cannot be held – the arcsine has no solution.