# What is the crosswind component?

Splits a reported wind into its crosswind and headwind (or tailwind) components for a runway, from the runway number, the wind direction and the wind speed, with the gust crosswind.

- Page: https://www.acalculator.org/physics/crosswind-calculator
- JSON spec: https://www.acalculator.org/physics/crosswind-calculator.json
- Version: b1ffc3fb76b2

## Default answer

Example with the default inputs (Runway 27, Wind direction 300, Wind speed 15 kn): On runway 27 with wind from 300° at 15 kn, the crosswind is 7.5 kn and the headwind 13 kn.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| rwy | Runway | The runway number, from 1 to 36: its heading in tens of degrees (runway 27 points 270°). |
| dir | Wind direction | The direction the wind blows from, in degrees, from 1 to 360 (360 is north). |
| ws | Wind speed | The steady wind speed. |
| g | Gusts | The gust speed, if the report gives one. Leave empty if there are none. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| crosswind | Crosswind | The part of the wind across the runway: speed × \|sin(angle)\|. |
| side | Crosswind from | Which side of the runway the crosswind comes from. |
| headwind | Headwind | The part of the wind along the runway: speed × cos(angle); negative is a tailwind. |
| along | Along the runway | Headwind, tailwind or none. |
| angle | Wind angle off the runway | The angle between the wind direction and the runway heading, from 0° to 180°. |
| gustCrosswind | Gust crosswind | The gust speed × \|sin(angle)\|. |

## Method

Angle = wind direction − runway number × 10, taken from −180° to 180°; crosswind = speed × |sin(angle)| (from the right when the angle is positive); headwind = speed × cos(angle), negative for a tailwind.

## Assumptions

- The runway heading is its number × 10 degrees. Real runway headings can differ by a few degrees from the number.
- The wind direction and the runway use the same reference (both magnetic, as ATIS and the tower give winds).

## Worked examples

1. rwy = 27, dir = 300, ws = 10.288889 gives crosswind = 5.144444, side = The right, headwind = 8.910439, angle = 30. Source: FAA, Pilot’s Handbook of Aeronautical Knowledge (FAA-H-8083-25C), Chapter 11 Aircraft Performance, Crosswind and Headwind Component Chart, https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/phak.
2. rwy = 9, dir = 180, ws = 15.433333 gives crosswind = 15.433333, headwind = 0, side = The right, along = None. Source: University of British Columbia, ATSC 113 Crosswinds and Headwinds (aircraft heading 90°, wind from 180° at 30 knots: zero headwind, 30 knot crosswind from the right), https://www.eoas.ubc.ca/courses/atsc113/flying/met_concepts/02-met_concepts/02d-crosswind/index.html.
3. rwy = 36, dir = 40, ws = 15.433333, g = 20.577778 gives crosswind = 9.920355, headwind = 11.822619, gustCrosswind = 13.227141, angle = 40. Source: FAA, Pilot’s Handbook of Aeronautical Knowledge (FAA-H-8083-25C), Chapter 11 Aircraft Performance, Crosswind and Headwind Component Chart, https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/phak.
4. rwy = 18, dir = 330, ws = 5.144444 gives crosswind = 2.572222, side = The right, headwind = -4.45522, along = Tailwind. Source: FAA, Pilot’s Handbook of Aeronautical Knowledge (FAA-H-8083-25C), Chapter 11 Aircraft Performance, Crosswind and Headwind Component Chart, https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/phak.

## FAQ

### How do I calculate the crosswind component?

Find the angle between the wind direction and the runway heading, then multiply the wind speed by the sine of that angle. On runway 27 (270°) with wind from 300° at 20 kn, the angle is 30° and the crosswind is 20 × sin 30° = 10 kn from the right.

### How do I calculate the headwind component?

Multiply the wind speed by the cosine of the angle. In the example above, 20 × cos 30° = 17.3 kn of headwind. Past 90° off the nose the cosine is negative, so the wind becomes a tailwind.

### Is there a quick rule of thumb?

Pilots often use the clock method: 15° off is about a quarter of the wind across, 30° half, 45° three quarters, and 60° or more nearly all of it. The exact sines are 0.26, 0.50, 0.71 and 0.87, which is what this page uses.

### Should I use the gust speed?

The steady wind gives the usual components. Gusts push the crosswind higher for moments, so it is worth checking the gust crosswind against your limit too. Type the gusts and the page shows it.

### Why does the runway number times 10 not match the real heading?

Runway numbers are the magnetic heading rounded to the nearest 10°, so runway 27 can point anywhere from about 265° to 275°. The difference changes the answer only a little, so allow a small margin.

### Should the wind be magnetic or true?

Use the same reference as the runway. Runway numbers are magnetic, and ATIS and tower winds are magnetic too; winds in METARs and forecasts are true, so correct them by the local magnetic variation first.

## Sources

- FAA, Pilot’s Handbook of Aeronautical Knowledge (FAA-H-8083-25C, 2023), Chapter 11 Aircraft Performance: Crosswind and Headwind Component Chart. https://www.faa.gov/regulations_policies/handbooks_manuals/aviation/phak (retrieved 2026-10-01)
- University of British Columbia, ATSC 113 Crosswinds and Headwinds: an aircraft heading 90° with wind from 180° at 30 knots has zero headwind and a 30 knot crosswind from the right. https://www.eoas.ubc.ca/courses/atsc113/flying/met_concepts/02-met_concepts/02d-crosswind/index.html (retrieved 2026-10-01)