Crosswind Component Calculator
The clock rule is a knot or two optimistic at 45°.
Work out Crosswind Component. The clock rule is a knot or two optimistic at 45°. States the assumption instead of hiding it.
Crosswind from the right
17.3 kt
10 kt headwind · 60° off the runway
The clock rule — 30° is a half, 45° is two-thirds, 60° is nearly all — is close enough to fly a circuit by and not close enough to decide a limit by. Showing both is the point: the error is a knot or two, and it is always on the optimistic side at 45°. Gusts are what the limit should be checked against, not the steady wind. A 15 kt wind gusting 25 is a 25 kt crosswind at the moment it matters, and that moment is usually in the flare. Wind is reported true by most automated services and magnetic by tower controllers, and the difference is the local variation. Getting that backwards on a day with 15° of variation moves the computed crosswind noticeably.
How the Crosswind Component Calculator works
Crosswind and headwind components for a runway, with the gust figure checked against a demonstrated limit and the clock rule shown next to the trigonometry.
Also known as: crosswind for runway 09 · clock rule crosswind · is this within my crosswind limit · headwind component from wind
Frequently asked questions
How do you calculate a crosswind component?
Wind speed times the sine of the angle between the wind and the runway. The headwind component is the same speed times the cosine.
What is the clock rule?
Treat the angle in degrees as minutes on a clock face: 15° is a quarter, 30° a half, 45° three-quarters, 60° and beyond effectively all. It is close and consistently optimistic at 45°.
Should I use the steady wind or the gust?
The gust. A 15 kt wind gusting 25 is a 25 kt crosswind at the moment it matters, and that moment is usually in the flare.
Is the demonstrated crosswind a limit?
No. It is what a test pilot achieved on a certification day — not a structural limit and not a promise about you. Your own limit should be lower and should account for practice and surface.
Is the wind reported true or magnetic?
Both, depending who is telling you. Most automated broadcasts report true; tower controllers report magnetic. On a day with 15° of variation, getting it backwards moves the computed crosswind noticeably.
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