What this calculator does
A wind at an angle to your heading splits into two parts: the crosswind, which is the speed multiplied by the sine of the angle, and the headwind, which is the speed multiplied by the cosine. At 45 degrees the two are equal, each about 71% of the full wind.
The useful landmarks are worth remembering. At 30 degrees the crosswind is half the wind speed. At 60 degrees it is 87%. At 90 degrees it is all of it and the headwind component is zero. Those three figures cover most of what a pilot needs to judge in the air without a calculator.
The formula
The angle between the wind direction and your heading is converted to radians. The crosswind is the wind speed multiplied by the sine of that angle, and the along-track component is the speed multiplied by the cosine. An angle beyond 90 degrees gives a negative cosine, which is reported as a tailwind rather than a headwind.
| Term | Meaning |
|---|---|
| Crosswind component | The part of the wind blowing across your path, which is what limits a landing. |
| Headwind component | The part blowing directly against you. Beyond 90 degrees it becomes a tailwind. |
| Angle off heading | The difference between the wind direction and your heading, from 0 to 180 degrees. |
| Demonstrated crosswind | The maximum crosswind component a given aircraft type has been tested to, published in the flight manual. |
The inputs explained
| Field | What to enter |
|---|---|
| Wind speed (knots) | Wind speed in knots. |
| Angle between wind and heading (°) | Angle between the wind direction and your heading, in degrees. Beyond 90 the along-track component becomes a tailwind. |
When to use it
Assessing a landing
Aircraft have a demonstrated crosswind limit, and the component rather than the raw wind speed is what it is compared against.
Planning a flight leg
The headwind or tailwind component determines groundspeed and therefore fuel and time, while the crosswind sets the drift correction needed.
Sailing or cycling into wind
The same trigonometry applies to any heading relative to a wind, and the split is what determines how much is resisting progress and how much is pushing sideways.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How does the angle split a 15 knot wind?
A fixed wind speed at a range of angles off the heading.
| Angle off heading | Crosswind component | Along-track component | Crosswind in km/h |
|---|---|---|---|
| 0° | 0.0 kt | 15.0 kt | 0.0 km/h |
| 30° | 7.5 kt | 13.0 kt | 13.9 km/h |
| 45° | 10.6 kt | 10.6 kt | 19.6 km/h |
| 60° | 13.0 kt | 7.5 kt | 24.1 km/h |
| 90° | 15.0 kt | 0.0 kt | 27.8 km/h |
Questions
How do I estimate crosswind in my head?
Divide the angle by 60 and use that fraction of the wind speed, capped at one. So 30 degrees gives half, 45 gives three quarters, and 60 or more gives all of it. Against the true figures of 50%, 71% and 87% that errs slightly high, which is the right direction to be wrong in.
What is a demonstrated crosswind limit?
The maximum crosswind component an aircraft type was tested with during certification, published in the flight manual. It is a demonstrated value rather than a structural limit, but treating it as a limit is standard practice and sensible for anyone not a test pilot.
What happens past 90 degrees?
The along-track component reverses and becomes a tailwind, which the calculator labels accordingly. A 135 degree wind gives an equal crosswind and tailwind. Tailwind on landing is generally far more limiting than crosswind, with typical limits around 10 knots.
Does gust speed matter?
Yes, and it is the figure to plan against. Calculate the component using the gust speed rather than the steady wind, since that is what you will have to handle at the worst moment. Many operators require exactly this.
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