How much wind is good for sailing? Wind strength and the Beaufort scale

For most cruising yachts, good sailing wind is force 3 to 5 Beaufort, about 7 to 21 knots. Beginners and families usually feel comfortable up to 4 Bft (16 kn), and experienced crews sail with a reef up to 6 Bft (27 kn). From 7 Bft most cruising sailors stay in harbour. The gusts count, not the mean wind.

What is the Beaufort scale?

The Beaufort scale divides wind strength into 13 forces, from 0 (calm) to 12 (hurricane). It goes back to the British naval officer Francis Beaufort and also describes each force by its effect on the sea, so you can estimate the wind by looking at the water.

Marine forecasts such as those of the DWD, Germany's national weather service, give the wind in Beaufort, while anemometers and weather models usually use knots or m/s. A knot is one nautical mile per hour, i.e. 1.852 km/h or about 0.51 m/s. As a rule of thumb, m/s times two gives roughly knots.

Beaufort scale: wind strength in knots, m/s and km/h

The values apply to the mean wind at 10 m height according to the WMO classification. The description of the sea applies to open water; under the lee of land and on inland lakes the waves stay smaller.

How much wind is good for beginners, families and experienced crews?

As a guideline: beginners 2 to 4 Bft, families with children 3 to 4 Bft, experienced crews on a cruising yacht 3 to 6 Bft with a reef. The limit depends on boat, crew, sailing area and waves, not just on the number.

Below 2 Bft a cruising yacht hardly makes progress, and the engine usually goes on. The waves count too: 4 Bft onshore with a short, steep sea feels harder than 5 Bft in the shelter of a coast. For a long beat to windward, allow one force less than for a reach, because the apparent wind is stronger upwind.

Why are gusts more important than the mean wind?

Because it is the gust that loads boat, rig and crew. Wind pressure rises with the square of the wind speed: twice the wind means four times the force. That is why you reef for the gusts.

A gust is the highest wind speed averaged over three seconds. Over open water, gusts are often 20 to 40 percent above the mean wind, and considerably more under the lee of land, in showers, at thunderstorm fronts and with fall winds such as the Bora. “South-west 4, gusts 6” in a marine forecast means: mean wind 11 to 16 kn, gusts 22 to 27 kn. More in the guide Gusts and thunderstorms.

What happens with wind against tide?

When the stream runs against the wind, the sea becomes shorter, steeper and higher than in the same wind without current. Even 4 to 5 Bft against a strong tidal stream produces a rough, sometimes breaking sea in tidal inlets, estuaries and straits.

Plan such places for the time when the stream runs with the wind or turns. How to do this is explained in the guide Tides and tidal streams.

How does Sailseer show wind and gusts?

Sailseer calculates the wind as a consensus of nine weather models and shows the gusts together with the range from the ensembles. You can set the unit to knots, Beaufort, km/h or m/s. Each leg is rated against your boat's gust and wave limits (default for a cruising yacht of 30 to 36 ft: 30 kn gusts and 2 m waves, both adjustable), and in tidal waters also for wind against tide. The sailing wind alert notifies you by email or push when wind in your preferred range is coming from the direction you want at your harbour. View the wind on the map. Official marine forecasts and warnings take precedence, and you set the limits for your boat and crew yourself.