Crosswind Component and Runway Selection

Updated: 2026-09-27 · First published: 2026-09-27 · About this site

Every landing is a vector problem. The wind rarely blows straight down the runway, so the reported wind has to be split into the part that helps you (headwind), the part that hurts you (tailwind) and the part that tries to push you off the centreline (crosswind). Pilots have been taught a dozen shortcuts for this; the point of this guide is to show which are accurate, which are safe approximations, and how the result drives the runway decision.

The geometry

Let θ be the angle between the wind direction and the runway heading, and V the wind speed. Then:

Crosswind component = V × sin θ
Headwind component = V × cos θ (negative means tailwind)

With wind 240° at 18 kt on runway 27 (heading 270°): θ = 30°. Crosswind = 18 × 0.50 = 9 kt; headwind = 18 × 0.87 = 16 kt. The wind is from the left of the runway heading (240 is anticlockwise from 270), so it is a 9 kt left crosswind.

Shortcuts and how much they lie

Angle θ	sin θ (exact)	Clock rule	Error
15°	0.26	¼ (0.25)	none
30°	0.50	½ (0.50)	none
45°	0.71	¾ (0.75)	slightly high — safe
60°	0.87	full (1.00)	high — safe
90°	1.00	full	none

The clock rule (angle in degrees read as minutes past the hour, fraction of the hour = fraction of the wind) over-estimates between 45° and 90°, which is the right direction to err. The other common shortcut — "half the wind at 30°, all of it at 60°" — is the same rule with fewer steps. Use whichever you can do reliably while flying the aeroplane.

Gusts

24018G30KT gives two speeds. The steady 18 kt component tells you the average crosswind; the gust 30 kt component tells you the peak you will have to counter in the flare. At 30° that is 9 kt steady, 15 kt in gusts. A rule used widely in training: compare the gust component with your personal limit, because the aircraft does not care about averages when the gust hits at 20 ft. Some operators add half the gust increment to the approach speed for the same reason.

Variable wind

24012KT 200V280 means the direction varied between 200° and 280° during the observation. Compute the crosswind for the worst extreme in your runway's sense. For runway 27, 200° gives θ = 70° and a crosswind of 12 × 0.94 = 11 kt — not the 6 kt the mean direction suggests. VRB05KT with no range means the direction is undefined; treat the whole 5 kt as potential crosswind on any runway.

Choosing the runway

Eliminate tailwinds first. A 10 kt tailwind increases landing distance by roughly 20% or more for a light aircraft, and many aircraft have a hard tailwind limit (often 10 kt). This is the component most likely to cause an overrun, not the crosswind.
Compare crosswinds among the remaining runways. Lower wins, but only if the difference is meaningful.
Then apply everything else: runway length, surface, approach aids, terrain, circuit direction, noise abatement, and what ATC is actually using. A slightly higher crosswind on the ILS runway may be the better choice in low cloud.

Every airport page on this site does this arithmetic from the live METAR for every runway end, ranks them, and draws the components on a compass. Try it on a field with several runway orientations, such as EHAM Amsterdam Schiphol or KJFK New York JFK, and compare it with what the TAF says the wind will do over the next hours.

True versus magnetic

METAR and TAF winds are given in degrees true. Runway numbers are magnetic. In Western Europe and the eastern Mediterranean the difference is a few degrees and does not change the answer; in Alaska, northern Canada or New Zealand it can be 15–25° and does. ATIS and tower wind is given in magnetic, which is why the tower's wind can differ from the METAR by exactly the local variation.

When the answer is "not today"

Set your own limit before you fly, in writing, and treat it as a limit rather than a target. The demonstrated crosswind for a typical two-seat trainer is around 15 kt; an instructor with 2,000 hours on type may land it in more, but that is not what the number in the AFM promises. If the gust component exceeds your limit on the best runway, the correct calculation ends with a diversion — and the neighbouring fields are one click away in the airport directory.

Frequently asked questions

What is the formula for crosswind component?

Crosswind = wind speed × sin(angle between wind direction and runway heading). Headwind = wind speed × cos(angle). Use the runway's magnetic heading and the METAR wind is in true degrees outside the US ATIS, so apply variation where it matters.

What is the clock-face rule?

Treat the angle between wind and runway as minutes on a clock: 15° = ¼ of the wind speed, 30° = ½, 45° = ¾, 60° or more = the full speed. It errs on the safe side and is easy to do on final.

Do I calculate crosswind with the gust or the steady wind?

Both. Most manufacturers' demonstrated crosswind figures are based on the steady wind, but the gust is what you will fight in the flare. Many operators and flight schools apply limits to the gust value; check your own SOP.

What is a demonstrated crosswind?

The highest crosswind at which the manufacturer's test pilots demonstrated the aircraft could be landed during certification — typically 15–17 kt for light singles. It is not a limit unless your operator or the AFM says it is, but exceeding it means you are outside demonstrated capability.

Which runway should I choose if two have similar crosswind?

The one with the headwind component, then the longer one, then the one with the better approach aids. A tailwind adds to ground speed and landing distance far more than the same headwind subtracts.