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Every aircraft has a maximum demonstrated crosswind, and every pilot needs a quick way to check a reported wind against it. The wind rarely blows straight down the runway, so we split it into two parts: the headwind (or tailwind) component along the runway, and the crosswind component across it.
Our Crosswind & Headwind Calculator does this instantly. Below is the maths behind it and a mental method you can use in the cockpit.
Step 1: Find the wind angle
The wind angle is the difference between the wind direction and the runway heading. For runway 12 (heading about 120°) with wind from 150°, the angle is 30°. Runway numbers are magnetic headings rounded to the nearest 10°, so use the actual published runway heading where you can.
Make sure both numbers use the same reference. Tower and ATIS winds are magnetic. METAR and TAF winds are true. In places with large magnetic variation, mixing them can give a misleading answer.
Step 2: Apply the formula
- Crosswind = wind speed × sin(wind angle)
- Headwind = wind speed × cos(wind angle)
If the headwind result is negative (wind angle more than 90°), it is a tailwind.
Worked example
Runway 12 (120°), wind 150° at 20 knots. Angle = 30°.
- Crosswind = 20 × sin 30° = 20 × 0.5 = 10 knots
- Headwind = 20 × cos 30° = 20 × 0.866 = 17.3 knots
The wind comes from the right of the runway heading (150° is clockwise of 120°), so this is a 10-knot crosswind from the right.
The clock-face rule of thumb
Without a calculator, use the wind angle as minutes on a clock face. The fraction of the hour gives the approximate crosswind fraction:
| Wind angle | Clock | Crosswind ≈ | Exact sin |
|---|---|---|---|
| 15° | quarter past | 1/4 of wind | 0.26 |
| 20° | 20 past | 1/3 of wind | 0.34 |
| 30° | half past | 1/2 of wind | 0.50 |
| 45° | quarter to | 3/4 of wind | 0.71 |
| 60° or more | full hour | all of the wind | 0.87–1.00 |
The rule slightly overestimates at 45° and 60°, which errs on the safe side. For the headwind, a simple memory aid is that at 30° you still have about 90% of the wind as headwind, at 45° about 70%, and at 60° half.
Gusts
When the wind is gusting, for example 15020G32KT, calculate the crosswind for the gust value as well. With a 30° angle, the steady crosswind is 10 knots, but the gust crosswind is 16 knots. Many operators compare the gust value against crosswind limits. Our calculator accepts an optional gust speed for this reason.
Tailwind
If the wind angle is more than 90°, you have a tailwind component. Wind from 270° at 10 knots on runway 09 is a direct 10-knot tailwind. Tailwind limits are often only 10 knots, and a tailwind increases landing distance significantly, so a runway change is usually preferable.
Checklist
- Confirm whether the wind is true or magnetic.
- Use the actual runway heading, not just the runway number × 10.
- Calculate for both the steady wind and the gust.
- Compare with your aircraft’s limits and your personal limits, which may be lower.
Try a few examples in the calculator, then check whether your mental estimate was within a couple of knots. To get the reported wind in the first place, see How to Read a METAR and TAF.
Educational content only. Follow your aircraft flight manual and operator procedures.
Worked example with a gust
Runway 27 (heading about 270°), wind 300/15G25KT. The wind is 30° off the runway.
- Steady wind: headwind = 15 × cos 30° ≈ 13 kt; crosswind = 15 × sin 30° = 7.5 kt from the right.
- Gust: headwind = 25 × cos 30° ≈ 21.7 kt; crosswind = 25 × sin 30° = 12.5 kt from the right.
- Compare the gust crosswind, not only the steady value, with your own limit and the aircraft’s demonstrated crosswind.
Common mistakes
- Using the runway number as the heading. Runway 27 means a heading of about 270°, not 27°. In calculators, enter 270.
- Mixing true and magnetic directions. Runway headings and the wind in an ATIS or tower report are magnetic; the wind in a METAR or TAF is true. Where magnetic variation is large, convert before comparing.
- Ignoring the gust. The crosswind you must handle at touchdown is the gust value.
- Treating “maximum demonstrated crosswind” as a hard limit. In most light-aircraft POHs it is the highest crosswind tested during certification, not a structural or legal limit. It is still a sensible ceiling for most pilots; your personal limit may be lower.
- Forgetting a tailwind. If the wind is more than 90° off the runway heading, the “headwind” is a tailwind, which lengthens the landing distance considerably.
Sources and further reading
- FAA Airplane Flying Handbook (FAA-H-8083-3) (crosswind approach and landing)
- FAA Pilot’s Handbook of Aeronautical Knowledge (FAA-H-8083-25)
- AIM 7-1, Meteorology (wind in weather reports)
Sources checked November 2026. Rules differ between countries and change over time: for real flights, use the current publications of the authority that applies to you, your aircraft flight manual and your operator’s procedures.