Beaufort Number	Wind Speed Miles Per Hour	Wind Speed Kilometers Per Hour	Description
0	< 1	< 1.6	Calm: Still: Smoke will rise vertically.
1	1 - 3	1.6 - 4.8	Light Air: Rising smoke drifts, weather vane is inactive.
2	4 - 7	6.4 - 11.3	Light Breeze: Leaves rustle, can feel wind on your face, weather vane is inactive.
3	8 - 12	12.9 - 19.3	Gentle Breeze: Leaves and twigs move around. Light weight flags extend.
4	13 - 18	20.9 - 29.0	Moderate Breeze: Moves thin branches, raises dust and paper.
5	19 - 24	30.6 - 38.6	Fresh Breeze: Moves trees sway.
6	25 - 31	40.2 - 50.0	Strong Breeze: Large tree branches move, open wires (such as telegraph wires) begin to "whistle", umbrellas are difficult to keep under control.
7	32 - 38	51.5 - 61.2	Moderate Gale: Large trees begin to sway, noticeably difficult to walk.
8	39 - 46	62.8 - 74.0	Fresh Gale: Twigs and small branches are broken from trees, walking into the wind is very difficult.
9	47 - 54	75.6 - 86.9	Strong Gale: Slight damage occurs to buildings, shingles are blown off of roofs.
10	55 - 63	88.5 - 101.4	Whole Gale: Large trees are uprooted, building damage is considerable.
11	64 - 72	103.0 - 115.9	Storm: Extensive widespread damage. These typically occur only at sea, and rarely inland.
12	> 73	> 115.9	Hurricane: Extreme destruction.

NOTE: The Beaufort number is also referred to as a "Force" number, for example, "Force 10 Gale".

To calculate knots, divide miles/hour by 1.15.

Small craft advisories are usually issued when force 6 is reached.