Ground Speed Calculator
Calculate ground speed, wind correction angle, and heading from true airspeed, wind speed, and wind direction using the aviation vector triangle.
What Is Ground Speed?
Ground speed is an aircraft's horizontal velocity relative to the ground. Pilots need it to estimate flight time and fuel. True airspeed (TAS) is speed through the surrounding air. Wind pushes the aircraft off course, so ground speed usually differs from TAS unless the air is still.
Vector Triangle for Ground Speed
Add the true airspeed vector and wind vector using the law of cosines. With course \(\delta\), wind direction \(\omega\) (where wind blows toward), true airspeed \(V_a\), and wind speed \(V_w\):
$$V_g = \sqrt{V_a^2 + V_w^2 + 2 V_a V_w \cos(\omega - \delta)}$$The wind correction angle \(\alpha\) keeps the aircraft on course:
$$\alpha = \arcsin\left(\frac{V_w}{V_a} \sin(\omega - \delta)\right)$$Heading is \(\psi = \delta + \alpha\), measured clockwise from north.
Aviation Examples
With 80 knot TAS and 20 knot wind, a direct tailwind gives 100 knot ground speed. A direct headwind gives 60 knots. Crosswind components require a heading correction so the track stays on the planned course.
Related tools: Crosswind Calculator and Windsock Calculator.
Frequently Asked Questions
What is the difference between TAS and ground speed?
TAS is speed relative to the air mass. Ground speed is speed relative to the Earth. Wind makes them differ unless the air is calm.
What is wind correction angle?
It is the angle you point the nose into the wind so the aircraft track matches the desired course over the ground.
Is wind direction where it comes from or goes to?
This calculator uses direction the wind blows toward, measured clockwise from north. A north wind (from the north) has direction 180 degrees.
Can ground speed be less than true airspeed?
Yes with a headwind component. A strong enough tailwind can also make ground speed greater than true airspeed.
Why do pilots care about ground speed?
It determines how long a trip takes and how much fuel is burned over the route, which affects scheduling and safety margins.
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