Crosswind calculator
Load an airfield (optional)
Headwind
11 kt
Crosswind from the right
10 kt
How crosswind is calculated
What matters is the angle between the wind and the runway. A wind straight down the runway is all headwind. The further it swings to the side, the more of it becomes crosswind, and at 90 degrees it is nothing but crosswind. Beyond that the headwind turns into a tailwind.
Mathematically the crosswind is the wind speed times the sine of the angle, the headwind the wind speed times the cosine. 20 kt at 30 degrees to the runway gives 10 kt of crosswind and about 17 kt of headwind.
The rule of thumb
Nobody has a calculator on final. The clock rule does the job: 15 degrees off gives a quarter of the wind speed as crosswind, 30 degrees half, 45 degrees three quarters, 60 degrees and more the full speed.
| Angle to the runway | Rule of thumb | Exact |
|---|---|---|
| 15° | ¼ | 26% |
| 30° | ½ | 50% |
| 45° | ¾ | 71% |
| 60° | 1 | 87% |
| 90° | 1 | 100% |
True or magnetic?
A METAR gives the wind direction relative to true north. Tower and ATIS give it magnetic, like the runway designator. In Germany the difference is currently about 2 to 6 degrees east. That shifts the components by a knot or two at most, but at the airfield the tower's wind is the one that counts.
The weather as a map
The METARMAP fetches the METARs of around 80 airfields every five minutes and shows each one as an LED in its GAFOR colour.