Windsock Calculator

How to Read a Windsock to Estimate Wind Speed

A windsock is a simple yet effective tool used to determine both wind direction and approximate wind speed. Typically found at airports, helipads, chemical plants, and highways, windsocks align themselves with the wind. The direction the windsock points shows where the wind is blowing towards. For example, if a windsock points south, the wind is blowing from the north.

To estimate the wind speed, you look at how much the windsock is inflated and extended. Standard windsocks, such as those certified by the Federal Aviation Administration (FAA), are designed with five alternating colored bands (usually orange and white, or red and white). Each band that is fully extended and horizontal indicates a specific increment of wind speed.

Windsock Extension and Wind Speed Rules

For a standard FAA-certified windsock, the wind speed corresponds to the number of segments extended as follows:

• 0 Segments (Limp): Wind speed is less than 3 knots (3.5 mph / 5.6 km/h).
• 1 Segment: Winds are around 3 knots (3.5 mph / 5.6 km/h).
• 2 Segments: Winds are around 6 knots (6.9 mph / 11.1 km/h).
• 3 Segments: Winds are around 9 knots (10.4 mph / 16.7 km/h).
• 4 Segments: Winds are around 12 knots (13.8 mph / 22.2 km/h).
• 5 Segments (Fully Extended): Wind speed is 15 knots (17.3 mph / 27.8 km/h) or higher.

The mathematical approximation for the wind speed in knots based on the number of extended segments $n$ is:

$$Wind\ Speed\ (knots) = 3 \times n$$