Convert a wind speed to its Beaufort force, or pick a Beaufort force to see the matching wind speed range, official name, and the effects seen at sea and on land.

Wind speed

Full Beaufort scale reference

Force	km/h	Knots	Name	At sea	On land
0	0-1	0-1	Calm	Sea like a mirror	Smoke rises straight up
1	1-5	1-3	Light air	Ripples, no foam crests	Smoke drifts, wind vanes still
2	6-11	4-6	Light breeze	Small wavelets, glassy crests	Wind felt on face, leaves rustle
3	12-19	7-10	Gentle breeze	Larger wavelets, some whitecaps	Leaves and twigs move constantly, flags extend
4	20-28	11-16	Moderate breeze	Small waves, frequent whitecaps	Dust and loose paper raised, small branches move
5	29-38	17-21	Fresh breeze	Moderate waves, many whitecaps, some spray	Small leafy trees sway
6	39-49	22-27	Strong breeze	Large waves, whitecaps everywhere, more spray	Large branches move, umbrellas hard to use
7	50-61	28-33	Near gale	Sea heaps up, foam blown in streaks	Whole trees sway, hard to walk against the wind
8	62-74	34-40	Gale	Moderately high waves, foam streaks well marked	Twigs break off trees, walking is difficult
9	75-88	41-47	Strong gale	High waves, dense foam, visibility reduced by spray	Minor damage to roofs and chimneys
10	89-102	48-55	Storm	Very high waves, sea surface white, poor visibility	Trees uprooted, considerable structural damage
11	103-117	56-63	Violent storm	Exceptionally high waves, ships hidden in wave troughs	Widespread damage to structures
12	118+	64+	Hurricane	Air filled with foam and spray, sea entirely white	Severe and widespread destruction

A scale born from the Royal Navy

The Beaufort scale was devised in 1805 by Francis Beaufort, a Royal Navy officer who later became the Admiralty's hydrographer. He needed a consistent, wind-speed-independent way for ship captains to log wind conditions, so he described each force by how a fully rigged man-of-war would handle it, from bare steerage way in calm air to conditions where no canvas could be carried at all. The Royal Navy adopted it as standard practice in 1838, and it was later extended to observations on land and matched to measured wind speeds, becoming the basis for the international scale still used by the World Meteorological Organization today.

The 13 forces at a glance

Force	km/h	Knots	Name
0	0-1	0-1	Calm
1	1-5	1-3	Light air
2	6-11	4-6	Light breeze
3	12-19	7-10	Gentle breeze
4	20-28	11-16	Moderate breeze
5	29-38	17-21	Fresh breeze
6	39-49	22-27	Strong breeze
7	50-61	28-33	Near gale
8	62-74	34-40	Gale
9	75-88	41-47	Strong gale
10	89-102	48-55	Storm
11	103-117	56-63	Violent storm
12	118+	64+	Hurricane

How it is used today

Marine and coastal weather forecasts still quote wind in Beaufort force alongside or instead of raw speed, because it ties a number directly to sea state and to what a boat crew or coastal resident can expect to feel. Shipping forecasts, small craft warnings, and gale warnings issued by the Met Office and other national weather services are built around these force thresholds, and the scale remains a quick shorthand for judging whether conditions are safe for sailing, fishing, or being out on open water.

Where the scale falls short

The Beaufort scale was designed around sea state, so its land-based effects are a later approximation rather than an exact match: a hedge-sheltered garden and an exposed hilltop can experience very different conditions at the same measured wind speed. Local relief, buildings, and vegetation all change how a given force actually feels on the ground, so treat the land descriptions as a general guide rather than a precise prediction, and check official Met Office wind warnings for anything safety related. See also our wind chill calculator to find out how a given wind speed affects the felt temperature in cold weather.