Airfield windsocks in many countries follow an FAA/ICAO pattern of five alternating stripes. The sock is designed so that each additional segment that fills and lifts corresponds to roughly 3 knots more wind. Pilots use it to estimate wind direction and strength before take-off and landing.
How to use the Windsock Calculator
- Inflated segments
Results update as you type, and every field accepts the units shown in its menu.
How it works
Count how many segments are filled and standing out from the pole, including partly lifted ones as fractions.
Tips
- Use your own measured figures – fuel economy, speed and prices vary a lot with driving style, traffic, load and season.
- Pick the unit in each field’s menu (miles or kilometres, mpg or L/100 km); the calculator converts everything for you.
- Fill up to the brim twice and divide the distance by the fuel added to measure real fuel economy.
- For vehicle modifications, treat results as a starting point and confirm with the parts maker or a professional mechanic.
Common mistakes to avoid
- Mixing US and imperial (UK) gallons – a UK gallon is about 20% bigger.
- Using the advertised fuel economy instead of real-world figures.
- Forgetting tolls, parking and wear and tear when comparing driving with public transport.
Example values
How the main result changes when Inflated segments changes and everything else stays at the example values above:
| Inflated segments | Wind speed (knots) |
|---|---|
| 1.5 | 4.5 |
| 2.25 | 6.8 |
| 3 | 9 |
| 3.75 | 11.2 |
| 4.5 | 13.5 |
Formula
Wind speed ≈ 3 knots × number of inflated segments (maximum 15 kt)Worked example
Inputs — Inflated segments: 3.
Results — Wind speed = 9 knots; Description = Moderate breeze.
Frequently asked questions
How many knots is a full windsock?
A standard windsock fully extends at about 15 knots.
What does a limp windsock mean?
Calm or very light wind, under about 3 knots.
Which way is the wind blowing?
The sock points downwind – the wind is coming from the end attached to the pole.
What formula does the Windsock Calculator use?
Wind speed ≈ 3 knots × number of inflated segments (maximum 15 kt).