Use this ground speed calculator to combine true airspeed and wind using vector math and get ground speed, wind correction angle, required heading, and headwind/crosswind components with a clear wind FROM vs TOWARD setting.
Advanced options
How to use our Ground Speed Calculator
- Pick an Input method: use Course + wind direction to solve for Wind correction angle (WCA) and Required heading, or use Wind angle relative to heading to get ground-speed magnitude from a known heading setup.
- Enter True airspeed TAS (knots) (must be greater than 0).
- Enter Wind speed (knots) (0 is allowed).
- If you chose Course + wind direction, enter Course / desired track (degrees) and Wind direction (degrees).
- Open Advanced options and set Wind direction convention to match your source: aviation weather is usually the direction the wind comes FROM.
- If you chose Wind angle relative to heading, enter Aircraft heading (degrees) and Wind angle relative to heading (degrees) using the built-in definition (0 = tailwind, 180 = headwind, 90 = crosswind).
- (Optional) Change Angle unit (degrees or radians) and Number display format (Auto, Plain, Scientific) if you need a specific style.
- Click Calculate.
- Sanity-check the results: if wind speed is 0, then Ground speed should equal TAS, WCA should be 0, and the headwind and crosswind components should both be 0.
Definitions
True airspeed (TAS): How fast the aircraft moves through the air (not over the ground).
Ground speed (GS): How fast you move over the ground. This calculator reports it as a non-negative magnitude.
Course / desired track: The direction you want your path over the ground to go, measured clockwise from North (0 to 360).
Heading: The direction the aircraft nose points. In wind, heading can differ from course because you may need to point into the wind.
Wind direction (FROM vs TOWARD): Aviation weather usually reports the direction the wind comes FROM [2]. A math wind vector usually points where the wind blows TOWARD, which is 180 degrees different.
Headwind/tailwind component: The part of the wind along the course. Positive means headwind (slows ground speed), negative means tailwind (speeds it up).
Crosswind component: The part of the wind perpendicular to the course. Here, positive means the wind pushes you to the right of course, and negative means it pushes you to the left.
Wind correction angle (WCA): How many degrees you must turn from the course to keep the ground track on the course. Positive means turn right, negative means turn left.
Common mistakes and quick fixes
Mistake: Treating Wind direction (degrees) as where the wind blows TOWARD when your setting is Wind is FROM (or the reverse), causing a 180 degree flip.
Fix: In Advanced options, set Wind direction convention to match your source (METAR-style is usually FROM), then recalculate.
Mistake: Using the shortcut "GS = TAS plus/minus wind" when the wind is not exactly lined up with the Course / desired track (degrees) .
Fix: Use Course + wind direction mode and read the signed Headwind/tailwind component and Crosswind component ; crosswind creates a nonzero WCA and changes Required heading .
Mistake: Seeing Wind correction angle WCA as N/A and assuming the calculator failed.
Fix: Check Notes and warnings ; if the needed sideways correction is bigger than TAS (crosswind too strong), you cannot hold that exact course with that TAS, so heading and WCA are not defined.
Mistake: Entering angles in the wrong sense, like mixing up course (the path you want over the ground) with heading (where the nose points).
Fix: Check Input method and then recalculate. For course-holding problems, enter the desired Course / desired track and let the calculator output the Required heading .
Mistake: In Wind angle relative to heading mode, typing 0 degrees to mean headwind (a common assumption) even though the tool defines 0 as tailwind.
Fix: Check Input method and then recalculate. Use the built-in definition (0 = tailwind, 180 = headwind) and recheck whether the ground speed got faster (tailwind) or slower (headwind).
Mistake: Mixing true and magnetic angles between inputs (course, wind direction, heading).
Fix: Check Input method and then recalculate. Use one consistent angle system for all inputs; the math works either way, but the output only matches real navigation if everything is in the same system.
Limitations & Key Assumptions / Boundary Conditions
Wind-direction convention must match your data: If your Wind direction (degrees) is entered as FROM but the calculator is set to TOWARD (or vice versa), your answer can be off by 180 degrees.
Course-holding can be impossible: In course-based mode, if the crosswind is stronger than the available airspeed to cancel it (crosswind magnitude greater than TAS), the calculator will show WCA and heading as N/A and explain why in Notes and warnings.
Steady, flat-wind model: Assumes constant wind speed and direction and level flight for the moment being analyzed. Gusts, wind shear, turns, and changing altitude can change real ground speed and drift.
No magnetic variation correction: The Angle reference control is a reminder only. If you mix true and magnetic inputs, the computed heading will not match what you see on real charts or instruments.
Alternate wind-angle method is not a full flight-planning solve: The Wind angle relative to heading method returns ground-speed magnitude from a known angle setup, but it does not compute the heading required to hold a specific course unless you use the course-based input method.
Methodology
The calculator treats speeds as vectors (arrows): airspeed plus wind equals ground speed. In Course + wind direction mode, it solves the classic wind triangle used for navigation.
1) Angle cleanup and wind FROM vs TOWARD: Angles are wrapped to the 0 to 360 range for display. If you select wind FROM (common in aviation weather [2]), the calculator converts it to a wind-to direction by adding 180 degrees.
windToDeg = (windFromDeg + 180) mod 360
2) Wind components relative to the course (course-based mode): Let theta be the angle from the course to the wind-to direction (in radians). Then split the wind into an along-course part (head/tail) and a sideways part (crosswind).
theta = windToRad - courseRad
head = windSpeed * cos(theta)
cross = windSpeed * sin(theta)
Signs: head is positive for headwind and negative for tailwind. cross is positive when the wind pushes you to the right of course.
3) Wind correction angle and heading (course-based mode): To keep the ground track on the course, the aircraft must point into the wind to cancel sideways drift. The wind correction angle comes from the wind-triangle geometry.
WCA = asin( (windSpeed * sin(theta)) / TAS )
Feasibility check: if |(windSpeed*sin(theta))/TAS| is greater than 1, the needed correction is not physically possible at that TAS, so WCA and heading are reported as N/A.
headingDeg = (courseDeg + WCAdeg) mod 360
4) Ground speed along the course (course-based mode): Along-track ground speed equals the along-track part of airspeed minus the along-track wind component.
GS = TAS * cos(WCA) - windSpeed * cos(theta)
Alternate input method: wind angle relative to heading: If you provide the wind angle relative to the aircraft heading, the calculator can find ground-speed magnitude using vector addition (law of cosines form). Here phi is your wind angle where 0 = tailwind and 180 = headwind.
GS_mag = sqrt(TAS^2 + windSpeed^2 + 2*TAS*windSpeed*cos(phi))
Mini-example (course-based): TAS = 110 kn, course = 270 deg, wind speed = 15 kn, wind direction = 300 deg, convention = FROM. Convert to wind-to: 120 deg. Then theta = 120 - 270 = -150 deg. Crosswind = 15*sin(-150 deg) = -7.5 kn (pushes left). Head component = 15*cos(-150 deg) = about -13.0 kn (tailwind). WCA = asin((-7.5)/110) = about -3.9 deg, so required heading = 270 + (-3.9) = 266.1 deg. Ground speed = 110*cos(-3.9 deg) - 15*cos(-150 deg) = about 122.7 kn.