Module 13 - Meteorology
Beaufort Scale Lookup: Wind Force, Knots and Sailing Meaning
Quick answer
The Beaufort scale converts wind force into practical sea conditions. Force 7 is a near gale at 28-33 knots; 56 knots is Force 11, a violent storm.
- Focus on practical thresholds: Force 4 is moderate, Force 6 is strong, Force 7 is near gale.
- Use the scale with forecasts, not as a replacement for local judgement.
- For Day Skipper decisions, link the number to reefing, shelter, crew comfort, and sea room.
Active recall
Section 2 of 6
Explain the main idea from the Beaufort Scale in your own words.
The Beaufort Scale describes wind force from 0 (calm) to 12 (hurricane). It links wind speed in knots to the conditions you can observe at sea, such as wave size, whitecaps, spray, and whether a small yacht should reef or seek shelter.
For Day Skipper purposes, the most useful range is Force 3 to Force 7. Force 3-4 is often comfortable sailing, Force 5 is fresh and more demanding, Force 6 normally means reefing early, and Force 7 or above is near gale or gale conditions where most training and family cruising yachts should be in harbour.
Forecasts normally give wind direction and Beaufort force, not just knots. Learning the force numbers helps you turn a shipping forecast into practical decisions about passage timing, sail plan, crew comfort, and safe harbour options.
Force 4, a moderate breeze, is 11-16 knots and is often good sailing weather for a prepared cruising yacht. Force 6, a strong breeze, is 22-27 knots and should trigger conservative sail and passage decisions. Force 7 is near gale, Force 8 is gale, and Force 10 is storm force; whether to reef, continue or stay in harbour always depends on boat, crew, sea room, tide, visibility and shelter.
Beaufort force lookup
| Force | Name | Knots | mph | km/h | Sailing meaning |
|---|---|---|---|---|---|
| 0 | Calm | <1 | <1 | <1 | Sea like a mirror. |
| 1 | Light air | 1-3 | 1-3 | 1-5 | Ripples; little drive under sail. |
| 2 | Light breeze | 4-6 | 4-7 | 6-11 | Small wavelets and gentle sailing. |
| 3 | Gentle breeze | 7-10 | 8-12 | 12-19 | Large wavelets; comfortable for many crews. |
| 4 | Moderate breeze | 11-16 | 13-18 | 20-28 | Small waves and whitecaps; good sailing. |
| 5 | Fresh breeze | 17-21 | 19-24 | 29-38 | More demanding; many yachts prepare to reef. |
| 6 | Strong breeze | 22-27 | 25-31 | 39-49 | Large waves and spray; reef early on many cruising yachts. |
| 7 | Near gale | 28-33 | 32-38 | 50-61 | Sea heaps up; most training and family cruising plans should seek shelter. |
| 8 | Gale | 34-40 | 39-46 | 62-74 | Dangerous for small craft. |
| 9 | Strong gale | 41-47 | 47-54 | 75-88 | Severe conditions. |
| 10 | Storm | 48-55 | 55-63 | 89-102 | Very high waves; avoid being at sea. |
| 11 | Violent storm | 56-63 | 64-72 | 103-117 | Exceptional waves and dangerous survival conditions. |
| 12 | Hurricane force | 64+ | 73+ | 118+ | Extreme danger. |
- Force
- 0
- Name
- Calm
- Knots
- <1
- mph
- <1
- km/h
- <1
- Sea state / sailing note
- Sea like a mirror
- Force
- 1
- Name
- Light air
- Knots
- 1-3
- mph
- 1-3
- km/h
- 1-5
- Sea state / sailing note
- Ripples; little steerage under sail
- Force
- 2
- Name
- Light breeze
- Knots
- 4-6
- mph
- 4-7
- km/h
- 6-11
- Sea state / sailing note
- Small wavelets; gentle sailing
- Force
- 3
- Name
- Gentle breeze
- Knots
- 7-10
- mph
- 8-12
- km/h
- 12-19
- Sea state / sailing note
- Large wavelets; comfortable sailing
- Force
- 4
- Name
- Moderate breeze
- Knots
- 11-16
- mph
- 13-18
- km/h
- 20-28
- Sea state / sailing note
- Small waves and whitecaps; good sailing
- Force
- 5
- Name
- Fresh breeze
- Knots
- 17-21
- mph
- 19-24
- km/h
- 29-38
- Sea state / sailing note
- Moderate waves; many yachts reef soon
- Force
- 6
- Name
- Strong breeze
- Knots
- 22-27
- mph
- 25-31
- km/h
- 39-49
- Sea state / sailing note
- Large waves and spray; reef early
- Force
- 7
- Name
- Near gale
- Knots
- 28-33
- mph
- 32-38
- km/h
- 50-61
- Sea state / sailing note
- Sea heaps up; seek shelter
- Force
- 8
- Name
- Gale
- Knots
- 34-40
- mph
- 39-46
- km/h
- 62-74
- Sea state / sailing note
- Moderately high waves; dangerous for small craft
- Force
- 9
- Name
- Strong gale
- Knots
- 41-47
- mph
- 47-54
- km/h
- 75-88
- Sea state / sailing note
- High waves; severe conditions
- Force
- 10
- Name
- Storm
- Knots
- 48-55
- mph
- 55-63
- km/h
- 89-102
- Sea state / sailing note
- Very high waves; avoid being at sea
- Force
- 11
- Name
- Violent storm
- Knots
- 56-63
- mph
- 64-72
- km/h
- 103-117
- Sea state / sailing note
- Exceptional waves; dangerous survival conditions
- Force
- 12
- Name
- Hurricane force
- Knots
- 64+
- mph
- 73+
- km/h
- 118+
- Sea state / sailing note
- Air filled with spray; extreme danger
| Force | Name | Knots | mph | km/h | Sea state / sailing note |
|---|---|---|---|---|---|
| 0 | Calm | <1 | <1 | <1 | Sea like a mirror |
| 1 | Light air | 1-3 | 1-3 | 1-5 | Ripples; little steerage under sail |
| 2 | Light breeze | 4-6 | 4-7 | 6-11 | Small wavelets; gentle sailing |
| 3 | Gentle breeze | 7-10 | 8-12 | 12-19 | Large wavelets; comfortable sailing |
| 4 | Moderate breeze | 11-16 | 13-18 | 20-28 | Small waves and whitecaps; good sailing |
| 5 | Fresh breeze | 17-21 | 19-24 | 29-38 | Moderate waves; many yachts reef soon |
| 6 | Strong breeze | 22-27 | 25-31 | 39-49 | Large waves and spray; reef early |
| 7 | Near gale | 28-33 | 32-38 | 50-61 | Sea heaps up; seek shelter |
| 8 | Gale | 34-40 | 39-46 | 62-74 | Moderately high waves; dangerous for small craft |
| 9 | Strong gale | 41-47 | 47-54 | 75-88 | High waves; severe conditions |
| 10 | Storm | 48-55 | 55-63 | 89-102 | Very high waves; avoid being at sea |
| 11 | Violent storm | 56-63 | 64-72 | 103-117 | Exceptional waves; dangerous survival conditions |
| 12 | Hurricane force | 64+ | 73+ | 118+ | Air filled with spray; extreme danger |
Apply it
Turn a forecast force into a decision
The inshore forecast increases from Force 4 to Force 6 during a passage with an inexperienced crew and a wind-against-tide headland.
- 1
Translate
Force 6 means a strong breeze, 22–27 knots of mean wind, before allowing for gusts and local acceleration.
- 2
Add context
Wind against tide can steepen the sea; crew ability, point of sail, daylight and sea room change the risk.
- 3
Set a trigger
Decide before departure whether to shorten, delay, seek shelter or reef early, and name the observation that triggers the change.
Sense check: The Beaufort number informs the decision; it does not produce one universal go/no-go answer for every vessel and crew.
Common mistakes
- Memorising numbers without linking them to sea state.
- Forgetting that gusts and local effects can make conditions feel stronger.
Quick practice check
Try a few questions before you move into the full module.
1. What does 'veering' mean in weather terminology?
2. What Beaufort force is a 'strong breeze'?
3. In the shipping forecast, what does 'soon' mean?
Key points
- Force 0: Calm (< 1 knot), sea like a mirror
- Force 3: Gentle breeze (7–10 kn), large wavelets
- Force 4: Moderate breeze (11–16 kn), small waves, whitecaps
- Force 5: Fresh breeze (17–21 kn), moderate waves, many whitecaps
- Force 6: Strong breeze (22–27 kn), large waves, spray. Reef sails.
- Force 7: Near gale (28–33 kn), sea heaps up. Seek shelter.
- Force 8+: Gale and above. Dangerous for small craft.
Common questions
What wind speed is Beaufort Force 4?
Beaufort Force 4, a moderate breeze, is 11-16 knots, about 13-18 mph or 20-28 km/h.
Is Force 4 good sailing weather?
Force 4 is often good sailing weather for a prepared cruising yacht, but the safe choice still depends on sea room, tide, visibility, crew experience and shelter.
What wind speed is gale force?
Gale force starts at Beaufort Force 8, which is 34-40 knots. Force 7 is a near gale.
Is Force 6 strong for sailing?
Force 6 is a strong breeze, 22-27 knots. Many cruising yachts reef early or change plans, but the safe choice depends on boat, crew, sea room and shelter.
What is Force 7 on the Beaufort scale?
Force 7 is a near gale, 28-33 knots. It is demanding for small craft and should be treated conservatively.
What wind speed is Force 10?
Force 10 is storm force, 48-55 knots. Small craft should avoid being at sea in those conditions.
What Beaufort force is 56 knots?
A sustained wind of 56 knots is Beaufort Force 11, violent storm. It is beyond ordinary small-craft sailing conditions.
What Beaufort force should a Day Skipper reef at?
Reefing depends on boat and crew, but Force 5 often prompts early preparation and Force 6 usually requires reefed sails on a cruising yacht.
Keep revising this topic
Sources and factual review
Reviewed 22 June 2026 - Day Skipper Revision.
Practice weather decisions
The meteorology module connects wind force, forecasts, pressure systems, fronts, and practical passage decisions.