Force

 Wind Speed

Description

Sea State

Knots

m/sec

0

  0 - 1

   0.0 - 0.2

 Calm

 Like a mirror

1

  1 - 3

   0.3 - 1.5

 Light Air

 Ripples only

2

  4 - 6

   1.6 - 3.3

 Light Breeze

 Small wavelets, not breaking

3

  7 - 10

   3.4 - 5.4

 Gentle Breeze

 Large wavelets, crests breaking,      white horses

4

 11 - 16

   5.5 - 7.9

 Moderate Breeze

 Small waves with frequent white horses

5

 17 - 21

   8.0 - 10.7

 Fresh Breeze

 Moderate waves, many white horses, some spray

6

 22 - 27

  10.8 - 13.8

 Strong Breeze

Large waves with white crests, some spray

7

 28 - 33

  13.9 - 17.1

 Near Gale

Sea heaping up, foam streaks blowing from crests

8

 34 - 40

  17.2 -20.7

 Gale

 High waves with crests breaking into spindrift

9

 41 - 47

  20.8 - 24.4

 Severe Gale

 High waves with tumbling crests, streaks of foam

10

 48 - 55

  24.4 - 28.4

 Storm

 Very high waves with long overhanging crests

11

 56 - 63

  28.5 - 32.6

 Violent Storm

 Exceptionally high waves, sea covered with foam

12

 64 Plus

  32.7 & Over

 Hurricane

 Air filled with foam, sea white with driving spray

NOTE:  It will be observed that there is a steady approximate ratio of 2 : 1 between metres per second and knots for each wind force in the Beaufort scale. In Danish and Swedish weather forecasts wind strength is given in metres per second, not in the Beaufort Scale.