Section 05 / Crosswind
Enter a wind and a runway number, or add a US airport ID to convert true wind to magnetic and use the real runway heading. See headwind and crosswind components, watch the wind triangle update live, and compare two runways before you decide.
Leave blank to enter everything yourself. Nothing is converted without an airport.
Enter wind speed and a runway number to see the diagram.
Why it works
The wind vector can be split into two perpendicular components using basic trigonometry. θ is the angle between the wind direction and the runway heading:
Crosswind = wind speed × sin(θ)
Headwind = wind speed × cos(θ)
At θ = 0° (wind straight down the runway), sin(0°) = 0 — no crosswind, all headwind. At θ = 90° (wind exactly perpendicular), sin(90°) = 1 — all crosswind, no headwind. The diagram makes this visible: the wind vector, headwind arrow, and crosswind arrow form a right triangle on every entry.
The number students get wrong
METARs report wind direction in degrees true. Runway numbers are magnetic — RWY 27 is approximately 270° magnetic, not true. At most U.S. airports the difference (magnetic variation) is 5–20°.
Without an airport ID, this calculator compares the two numbers you enter and converts nothing. Enter a METAR wind (true) against a painted runway number (magnetic) and the answer can be well off:
| Runway and true wind | Unconverted | Actual |
|---|---|---|
| KSEA 16L, 200° at 20 kt | 12.9 kt | 6.8 kt |
| PANC 15, 165° at 25 kt | 6.5 kt | 0 kt |
The PANC wind is blowing straight down the runway, yet the unconverted answer shows 6.5 kt of crosswind. The error doesn't always run high, either. With west variation it can hide crosswind: KDAB 07L with a true wind of 100° at 15 kt reads 7.5 kt, and the actual value is 8.6 kt.
Enter a US airport ID and the calculator does this for you and shows each step. Otherwise, convert a METAR wind before you enter it: subtract east variation, add west ("east is least, west is best"). ATIS, ASOS or AWOS voice broadcasts, and tower controllers already give wind in magnetic, so don't convert those. A painted runway number is also rounded, so use the runway's actual magnetic heading if you have it.
Actual values compare the true wind with each runway's true alignment in FAA airport data effective October 29, 2026.
On the checkride, examiners want to know you understand this distinction exists — not that you can calculate variation from memory.
Know your aircraft
Every POH includes a "demonstrated crosswind component" — the maximum crosswind the test pilot documented during certification. This is not a legal limit. The FAA does not publish a crosswind limit for light training aircraft.
| Aircraft | Demonstrated | Source |
|---|---|---|
| Cessna 152 | 12 kt | POH §5 |
| Cessna 172S | 15 kt | POH §5 |
| Piper PA-28-161 | 17 kt | POH §5 |
| Piper PA-28-181 | 17 kt | POH §5 |
Your proficiency, currency, runway surface, and CFI guidance set the practical limit — not the POH number alone.
Checkride connection
The ACS (PA.I.F — Preflight Assessment, Risk Management) expects you to select the most suitable runway as part of preflight decision-making. The crosswind component is one input. Runway length, slope, surface condition, obstructions, and traffic pattern are others.
The key ACS principle: show your reasoning, not just your answer. An examiner asking about runway selection wants to hear you work through the wind angle, your aircraft's demonstrated value, your own currency, and what you'd do if conditions change on final.
This tool shows components. The go/no-go decision is yours.