E6B Calc How to calculate crosswind and headwind components, including the gust
Crosswind is wind speed times the sine of the angle between wind and runway; headwind is the cosine of that same angle. Runway 27, wind 310° at 15 kt gusting 25: 10 kt of crosswind from the right, 11 kt headwind, and 16 kt in the gust. That last number is the one that catches pilots out on a gusty day — the steady wind looks fine, the gust doesn't. E6B Calc's free Crosswind screen flags it when you pass the limit you set.
When you need the crosswind component
Before every departure and arrival you weigh the wind against the runway in use and against what you and the aircraft can actually handle. The POH figure is a maximum demonstrated crosswind — what a test pilot showed, not necessarily a hard wall. Most pilots treat it as their own limit anyway, preferring to divert rather than find out the hard way where their own number actually sits.
The crosswind component calculation formula
- Angle = wind direction − runway heading.
- Crosswind = wind speed × sin(angle). In the app a positive result means the wind is from the right.
- Headwind = wind speed × cos(angle). A negative result is a tailwind.
- Gust crosswind = gust speed × sin(angle): the gust changes the size, not the angle.
Mental shortcut for the taxiway: 30° off the runway is roughly half the wind as crosswind, 45° about 70%, 60° about 90%. Past 60°, just call it all crosswind and move on.
How to calculate crosswind component in E6B Calc
- On E6B, open Crosswind under Flight.
- Pick the Wind reference: Magnetic (tower) for wind from the tower or ATIS, True (METAR) for wind from a METAR or TAF.
- Type the Runway heading in degrees, for example 270 for runway 27.
- Enter Wind from and Wind speed, and the Gust if there is one.
- Optionally type your Demonstrated crosswind so the app can flag a gust that goes past it.
- Read Crosswind, Head/tailwind and Crosswind in the gust. An Over the limit or Tailwind warning appears when it applies.
Worked examples
| Runway heading | Wind | Setting | Crosswind | Head/tailwind | Notes |
|---|---|---|---|---|---|
| 270° | 310° at 15 kt, gust 25 | Magnetic (tower), demonstrated 15 kt | 10 kt from the right | 11 kt headwind | 16 kt in the gust: Over the limit |
| 270° | 300° at 15 kt | True (METAR), variation 10 °E | 5 kt from the right | 14 kt headwind | Wind becomes 290° magnetic |
| 090° | 300° at 12 kt | Magnetic (tower) | 6 kt from the left | 10 kt tailwind | Tailwind warning |
Row one is the trap: steady crosswind is a comfortable 10 kt, fine by any measure, but the gust pushes it to 16, past the 15 kt limit you typed in. The app warns on the worse of the two numbers, not the nicer-looking one.
True or magnetic wind: the classic trap
Runways are numbered by magnetic heading. Tower and ATIS winds are magnetic too. METAR and TAF winds are not — they're true, full stop, and mixing the two is an easy way to fly a calculation that looks right and isn't. 10° of easterly variation turns a METAR wind of 300° into 290° magnetic, and the crosswind on runway 27 drops from about 8 kt to 5. Pick True (METAR), type the Magnetic variation (east positive), done.
From a METAR straight to crosswind
If you paste a METAR into the METAR & TAF Decoder and tap Use this report, you can add the runway heading and variation there. The decoder uses the reported gust automatically, so you see the worst case without typing the wind again.
Tips
- Round the runway number up to a heading: runway 17 is about 170°, but the real magnetic heading may be 168° or 173°. Use the published heading when you have it.
- A small crosswind with a strong tailwind can be the real problem: check Head/tailwind too.
- The Crosswind widget (E6B Pro) and the Apple Watch app show crosswind for a runway and wind you enter; neither downloads the wind.
Questions and answers
How do I calculate the crosswind component with a gust?
How do you calculate crosswind component without a chart?
Does the app know my runway?
Is this free?
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