Crosswind calculator
Enter the runway and the wind and see the crosswind and headwind in knots, gusts included, for both ends of the runway.
Enter a runway and a wind, for example runway 27 with a wind from 300 degrees at 20 knots.
Crosswind at a glance
Knots across the runway for each wind speed and angle off the runway, worked out with the same sums as the tool.
| Angle off the runway | 10 kt wind | 15 kt wind | 20 kt wind | 25 kt wind |
|---|---|---|---|---|
| 10° | 2 kt | 3 kt | 4 kt | 4 kt |
| 20° | 3 kt | 5 kt | 7 kt | 9 kt |
| 30° | 5 kt | 8 kt | 10 kt | 13 kt |
| 45° | 7 kt | 11 kt | 14 kt | 18 kt |
| 60° | 9 kt | 13 kt | 17 kt | 22 kt |
| 90° | 10 kt | 15 kt | 20 kt | 25 kt |
What crosswind and headwind mean
Aircraft take off and land into the wind where they can, because a headwind shortens the run. The wind rarely lines up with the runway, though. Some of it blows straight down the runway, the headwind, and some blows across it, the crosswind. A crosswind tries to push the aircraft sideways, so pilots need to know how strong it is before they land.
How it is worked out
First, find the angle between the wind and the runway. The crosswind is the wind speed times the sine of that angle, and the headwind is the wind speed times the cosine. For example: runway 27 points 270 degrees, and the wind is from 300 degrees at 20 knots, so the angle is 30 degrees. The sine of 30 degrees is exactly a half, so the crosswind is 10 knots from the right. The headwind is about 17 knots.
Many instructors teach a quick mental version called the clock method. Count 15 degrees off the runway as a quarter of the wind across, 30 degrees as half, 45 degrees as three quarters, and 60 degrees or more as all of it. It's an approximation for the cockpit; the calculator gives you the exact figure.
Runway numbers and wind directions
A runway's number is its direction to the nearest ten degrees, with the last zero dropped, so runway 27 points roughly west. The runway at the other end has the opposite number: 27 and 09 are the same strip of tarmac. Parallel runways add L, C or R for left, centre and right.
One thing to watch: runway numbers use magnetic north, and so does the wind the tower or ATIS gives you. The wind in a METAR uses true north. In the UK the difference between the two is small, but in some parts of the world it is many degrees, so use the tower's wind with the runway number when it matters.
Gusts
If the wind is gusting, put the gust in too. The calculator works out the crosswind at the steady wind and at the gust, because the gust is the one that catches you out in the last few feet. Always check your aircraft's handbook and your own or your instructor's limits.
A runway of your own
Pilots tend to have a favourite airfield. The airport code print sets its code in big type with the name and position beneath.