How this calculator works
The wind is a vector. Its angle relative to the runway heading decides how much of it blows across the runway and how much blows along it. Subtracting the runway heading from the wind direction gives the relative angle, and the sine of that angle gives the crosswind component while the cosine gives the headwind component. A negative headwind is a tailwind. The runway number is a magnetic heading in tens of degrees, so runway 27 points to 270 degrees. This tool uses the reported wind direction as magnetic; if your only wind is true, correct it for magnetic variation first.
Formula
relative angle = wind direction - runway heading, normalised to -180 to 180 degrees. Crosswind = wind speed x sin(relative angle). Headwind = wind speed x cos(relative angle). A negative headwind is a tailwind.
Worked example
Runway 09 has a heading of 090 degrees. A 20 knot wind from 135 degrees is 45 degrees off the nose, so the crosswind is 20 x sin 45 = 14.1 knots from the right and the headwind is 20 x cos 45 = 14.1 knots.
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Frequently asked questions
What is a safe crosswind limit?
It depends on the aircraft type, pilot experience, runway condition and the operator manual. This page only does the vector arithmetic. Compare the component with the aircraft flight manual and company limits, and remember that gusts and runway friction matter.
Why is a wind from the right called a right crosswind?
When the wind direction is clockwise from the runway heading, the air pushes the aircraft from its right side. A positive relative angle and a positive sine therefore mean a crosswind from the right.
Does the runway magnetic variation matter?
Yes. Runway numbers and reported winds are normally magnetic, so mixing a true wind with a magnetic runway heading gives the wrong angle. Apply the magnetic variation before entering the wind direction.
How do gusts change the result?
Use the reported gust value for a conservative check, because the instantaneous crosswind can exceed the mean wind. The table shows how quickly the crosswind grows as the relative angle moves away from the runway heading.