Ground Speed Calculator

Enter true airspeed, aircraft heading, and wind direction/speed to get ground speed, ground track, drift (wind correction) angle, and headwind/tailwind component using the wind-triangle vector method.

Quick Facts

Vector formula
GS = |V_TAS + V_wind|
Ground speed is the vector sum of the true-airspeed vector and the wind vector, not a simple add or subtract.
Wind convention
Direction wind blows FROM
Aviation wind direction is always the compass heading the wind is coming from, not where it is headed.
Drift angle
Drift = Track − Heading
Positive drift means the wind pushes the ground track to the right of the aircraft's heading.

Your Results

Calculated
Ground Speed
-
Speed over the ground (vector sum of TAS and wind)
Ground Track
-
True direction actually flown over the ground
Drift (Wind Correction) Angle
-
Angle between heading and ground track
Headwind/Tailwind Component
-
Wind component along the heading

Ready

Enter true airspeed, heading, and wind, then press Calculate.

Formula and Method for Ground Speed

Ground speed is how fast an aircraft (or any vehicle moving through a fluid medium) actually travels over the ground, as opposed to true airspeed (TAS), which is how fast it moves through the surrounding air mass. The two match only in still air. Whenever wind is present, the wind's velocity vector combines with the aircraft's airspeed vector, and the result — found using the classic "wind triangle" — gives both the ground speed and the actual track flown over the ground. This calculator performs that vector addition directly from true airspeed, heading, wind direction, and wind speed.

How the calculation works

Both the aircraft's motion through the air and the wind's motion are converted into north/east vector components. The airspeed vector points along the heading with magnitude TAS: VN = TAS·cos(heading), VE = TAS·sin(heading). Because wind direction is reported as the direction the wind blows FROM, the wind's actual velocity vector points 180° opposite that value: VN,wind = WS·cos(wind direction + 180°), VE,wind = WS·sin(wind direction + 180°). Adding the two vectors gives the ground velocity vector; its magnitude is the ground speed, GS = √(VN,total² + VE,total²), and its direction (via atan2) is the ground track. The drift, or wind correction angle, is simply track minus heading. Projecting the wind vector onto the heading direction gives the headwind (positive) or tailwind (negative) component along the flight path.

Common mistakes

  • Flipping the wind direction: weather reports and this calculator both use the direction the wind blows FROM. Treating it as the direction the wind blows TOWARD introduces a 180° error and reverses headwind and tailwind.
  • Confusing heading with track: heading is where the nose points; track (or course) is the path actually flown over the ground. They are equal only when there is no crosswind component.
  • Mixing true and magnetic directions: heading and wind direction must be in the same reference frame — both true or both magnetic — or the drift angle will be wrong.
  • Mismatched units: true airspeed and wind speed must use the same unit (knots, mph, km/h, or m/s) before they are combined; this calculator applies one unit to both.

Real-world applications

  • Dead-reckoning flight planning uses ground speed, not airspeed, to estimate time en route, fuel burn, and estimated time of arrival.
  • Pilots add the wind correction angle to their intended heading so that the resulting ground track matches the desired course over the ground.
  • Headwind and tailwind components help pilots judge takeoff/landing performance and choose favorable routes or altitudes with better winds aloft.
  • The same wind-triangle vector math applies to marine navigation (boat speed through water plus current) and drone flight planning in wind.

Frequently Asked Questions

What is the difference between true airspeed and ground speed?
True airspeed (TAS) is how fast the aircraft moves through the surrounding air mass. Ground speed is how fast it moves over the ground. The two are equal only when there is no wind; otherwise the wind vector adds to or subtracts from the airspeed vector to produce the ground speed.
How is wind direction defined in this calculator?
Wind direction uses the standard aviation and meteorological convention: it is the compass direction the wind is blowing FROM, not the direction it is blowing toward. A wind direction of 270° means the wind is coming from the west and blowing toward the east.
What is a wind correction angle (drift angle)?
The wind correction angle (also called drift angle here) is the difference between the aircraft's heading — where the nose points — and its actual ground track — the path it traces over the ground. Pilots add a wind correction angle to their heading so the resulting ground track matches the desired course.
Does this vector method work for boats or drones too?
Yes. The same wind-triangle vector math applies to any vehicle moving through a moving medium — replace true airspeed and wind with a boat's speed through water and the current, for example — as long as heading, speed relative to the medium, and the medium's direction and speed are known.

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