Windsock Calculator

A windsock is a conical, tubular fabric device used at airports, heliports, and other locations to simultaneously indicate wind direction and approximate wind speed. It points in the direction the wind is blowing toward, and its angle of elevation indicates how strong the wind is — from limp (calm) to fully horizontal (strong winds).

The angle the windsock makes with its pole indicates wind speed. At 0° it hangs straight down (no wind), while at 90° it is fully horizontal (wind of approximately 15 knots or more). For intermediate angles, wind speed in knots can be estimated as 15 × sin(angle). Alternatively, count the number of inflated segments — each represents roughly 3 knots.

Look at the windsock from the side. Note the angle it forms relative to its pole — this gives you wind speed. The open end of the windsock faces the direction the wind is coming from, and the closed end points downwind. Partial inflation (1–4 segments lit up) indicates lighter winds, while full horizontal extension signals winds at or above 15 knots.

A fully extended windsock (at 90° to the pole) indicates a wind speed of approximately 15 knots (about 17 mph or 28 km/h). This corresponds to roughly Beaufort Force 4–5. Standard aviation windsocks are designed so that full extension equals at least 15 knots.

Standard windsocks have 5 colored segments. Each inflated segment represents approximately 3 knots of wind speed. So 1 segment ≈ 3 knots, 2 segments ≈ 6 knots, 3 segments ≈ 9 knots, 4 segments ≈ 12 knots, and 5 segments (fully extended) ≈ 15 knots. This makes it easy to get a quick wind estimate without measuring the angle precisely.

A windsock works on the principle of aerodynamic drag. Wind enters the open (wide) end of the cone and exits through the narrow end, inflating the fabric. The balance between the wind force and gravity determines how far the sock lifts from vertical. Stronger winds push the sock higher toward horizontal, giving a visual indication of wind intensity.

The Beaufort scale is a numerical scale from 0 to 12 used to describe wind speed based on observed conditions. Force 0 is calm (less than 1 knot), Force 6 is a strong breeze (~25 knots), and Force 12 is hurricane force (64+ knots). A standard windsock fully extended corresponds to roughly Beaufort Force 4–5 (moderate to fresh breeze).

No — while windsocks are most commonly associated with airports and heliports, they are also used at chemical plants, industrial facilities, racetracks, and even some beaches and camping areas. Any location where knowing wind direction and approximate speed is important for safety may use a windsock.