Beaufort Scale Article Image

The Beaufort Scale

Measuring Wind Speed

RMetS Editor
19 July 2018

The Beaufort Scale is an empirical measure that relates wind speed to observed conditions at sea or on land. Its full name is the Beaufort wind force scale

Below is a table showing the Beaufort Scale with speeds in knots, miles per hour and kilometers per hour.

 

Wind Force

Description

km/h mph knots Specifications
0 Calm <1 <1 <1 Smoke rises vertically
1 Light Air 1-5 1-3 1-3 Direction shown by smoke drift but not by wind vanes
2 Light Breeze 6-11 4-7 4-6 Wind felt on face; leaves rustle; wind vane moved by wind
3 Gentle Breeze 12-19 8-12 7-10 Leaves and small twigs in constant motion; light flags extended
4 Moderate Breeze 20-28 13-18 11-16 Raises dust and loose paper; small branches moved.
5 Fresh Breeze 29-38 19-24 17-21 Small trees in leaf begin to sway; crested wavelets form on inland waters.
6 Strong Breeze 38-49 25-31 22-27 Large branches in motion; whistling heard in telegraph wires; umbrellas used with difficulty.
7 Near Gale 50-61 32-38 28-33 Whole trees in motion; inconvenience felt when walking against the wind.
8 Gale 62-74 39-46 34-40 Twigs break off trees; generally impedes progress.
9 Strong Gale 75-88 47-54 41-47 Slight structural damage (chimney pots and slates removed).
10 Storm 89-102 55-63 48-55 Seldom experienced inland; trees uprooted; considerable structural damage
11 Violent Storm 103-117 64-72 56-63 Very rarely experienced; accompanied by widespread damage.
12 Hurricane 118 plus 73 plus 64 plus Devastation