How to Measure Wind Speed: The Beaufort Wind Force Scale

February 25, 2008

Below is a wind chart, created by Admiral Beaufort. Beaufort arranged the numbers 0 to 12 to indicate the strength of the wind from calm (force 0) to hurricane (force 12). Here's a scale adapted to land:

“Used Mostly at Sea but of Help to All Who Are Interested in the Weather”

Beaufort Force Description When You See or Feel This Effect Wind (mph) Wind (km/h)
0 Calm Smoke goes straight up less than 1 less than 2
1 Light air Wind direction is shown by smoke drift but not by wind vane 1-3 2-5
2 Light breeze Wind is felt on the face; leaves rustle; wind vanes move 4-7 6-11
3 Gentle breeze Leaves and small twigs move steadily; wind extends small flags straight out 8-12 12-19
4 Moderate breeze Wind raises dust and loose paper; small branches move 13-18 20-29
5 Fresh breeze Small trees sway; waves form on lakes 19-24 30-39
6 Strong breeze Large branches move; wires whistle; umbrellas are difficult to use 25-31 40-50
7 Moderate gale Whole trees are in motion; walking against the wind is difficult 32-38 51-61
8 Fresh gale Twigs break from trees; walking against the wind is very difficult 39-46 62-74
9 Strong gale Buildings suffer minimal damage; roof shingles are removed 47-54 75-87
10 Whole gale Trees are uprooted 55-63 88-101
11 Violent storm Widespread damage 64-72 102-116
12 Hurricane Widespread destruction 73+ 117+


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How to measure wind speed

How to measure wind speed