Beaufort Scale Calculator
Updated recently with improved calculation accuracy and expanded examples.
Enter wind speed in knots, mph, km/h, or m/s to get the corresponding Beaufort force and sea state description.
Last updated: August 28, 2026
Author: OceanCalc Editorial Team · Publisher: Albor Digital LLC
Beaufort Scale Calculator
Result
Beaufort force
4
Formula
Force 0–12 from wind speed (kn). Force 5 = 17–21 kn, Force 7 = 28–33 kn.What is the Beaufort Scale Calculator?
The Beaufort scale is a 0–12 scale that describes wind speed by its effects on the sea and on objects. Force 0 is calm; force 12 is hurricane.
The scale was developed by Francis Beaufort. Each force has an associated sea state description (wave height, foam, visibility).
Beaufort scale
The Beaufort scale classifies wind strength by observed sea state and wind speed bands, giving mariners a common language for conditions.
Related Maritime Calculators
Overview
The Beaufort scale classifies wind strength by observed sea state and wind speed bands, giving mariners a common language for conditions. A Beaufort Scale Calculator is used in maritime navigation to perform precise calculations based on established nautical formulas. This tool allows you to apply your inputs to the stated nautical relationships using accurate and standardized methods.
Key takeaways
- Beaufort Scale Calculator — The Beaufort scale classifies wind strength by observed sea state and wind speed bands, giving mariners a common language for conditions.
- Formula — Beaufort force is defined by wind speed ranges (knots).
- How to use — Type your figures into the form; outputs refresh so you can compare cases quickly.
How to use
Type your figures into the form; outputs refresh so you can compare cases quickly.
Formula
Core relationship: Force 0–12 from wind speed (kn). Force 5 = 17–21 kn, Force 7 = 28–33 kn.
Beaufort force is defined by wind speed ranges (knots). Force 0: 0–1 kn; Force 3: 7–10 kn; Force 5: 17–21 kn; Force 7: 28–33 kn; Force 10: 48–55 kn; Force 12: 64+ kn.
The scale was developed by Francis Beaufort. Each force has an associated sea state description (wave height, foam, visibility).
Practical use cases
Beaufort Scale Calculator: passage planning, crew briefings, instrument-to-chart unit checks, and verifying mental math when tired or in rough weather.
Tips for accuracy
- Match input units to your chart, GPS, or instrument before trusting the Beaufort Scale Calculator.
- Cross-check important outputs with a second method or crew when visibility or motion is poor.
- Treat simplified models (waves, radar horizon, etc.) as estimates; real conditions vary.
Practical examples
- 10 kn → Force 3 (Gentle breeze)
- 20 kn → Force 5 (Fresh breeze)
- 30 kn → Force 7 (High wind)
- 50 kn → Force 10 (Storm)
Frequently Asked Questions
What is the Beaufort scale?
The Beaufort scale is a 0–12 scale that describes wind speed by its effects on the sea and on objects. Force 0 is calm; force 12 is hurricane. It is widely used in marine weather and forecasts.
How do you convert wind speed to Beaufort?
Wind speed ranges (in knots) are defined for each force. For example, Force 4 is 11–16 knots, Force 5 is 17–21 knots. Our calculator maps your entered wind speed to the correct Beaufort force and sea description.
What wind is Force 6?
Force 6 (Strong breeze) is 22–27 knots. Sea state: large waves, extensive white foam. Often used as a threshold for small craft advisory conditions.
How accurate is this calculator?
It uses standard maritime formulas and noted approximations. Use it for planning and checks; confirm safety-critical decisions with official sources.
Can I use this on mobile?
Yes. Layouts are responsive for phones and tablets on deck or in the cockpit.
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These calculations are based on standard maritime navigation formulas used in seamanship, chart navigation, and marine route planning.
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Results are estimates for educational purposes only and should not be used for real navigation decisions.