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Beaufort Wind Scale Converter

Science

Convert Beaufort wind force numbers (0-12) to wind speed in km/h, mph, knots, or m/s, and back — for sailors, meteorology students, and weather forecasts.

Reviewed by the thecalcu.com team · Last updated July 18, 2026

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What is a Beaufort Scale?

A Beaufort Wind Scale Converter translates between the Beaufort force number (0 to 12), the classic wind-strength scale used in maritime and weather forecasting, and standard wind speed units like km/h, mph, knots, and m/s. The Beaufort scale doesn't increase in even speed increments; it follows a power-law relationship where higher force numbers represent disproportionately larger wind speed increases, matching how wind's physical effects (wave height, tree movement) scale with force.

This converter applies the exact formula meteorologists use to relate Beaufort force to wind speed, making it distinct from the general Speed Converter, which handles standard linear speed unit conversions but has no Beaufort scale option.

Why Use a Beaufort Wind Scale Converter?

Marine weather forecasts, shipping bulletins, and some coastal warnings report wind conditions in Beaufort force rather than a raw speed figure, while most weather apps and instruments report wind speed in km/h or mph. Translating between the two, especially since the relationship is a power law, not a simple multiplier, requires the actual conversion formula rather than a rough estimate.

Two concrete situations this solves: converting a shipping forecast's "Beaufort force 7" warning into km/h or knots to understand the actual wind speed for sailing or fishing trip planning, and converting a weather station's measured wind speed into its Beaufort equivalent to cross-reference against a marine forecast's terminology.

Who Should Use This Converter?

  • Sailors and boaters translating marine shipping forecasts (given in Beaufort force) into the speed units their onboard instruments display.
  • Meteorology students learning the mathematical relationship between the historical Beaufort scale and modern wind speed measurement.
  • Fishermen and coastal workers checking Beaufort-based small-craft warnings against actual wind speed readings before heading out.
  • Weather enthusiasts and hobbyist forecasters cross-referencing Beaufort descriptions ("Fresh Breeze," "Near Gale") against numeric wind speed data.
  • Pilots and outdoor event planners interpreting wind warnings that reference Beaufort force in regions where it's still commonly used.

What Insights Does the Beaufort Scale Converter Give You?

Converting a Beaufort number to km/h, mph, knots, or m/s gives you the precise numeric wind speed behind a Beaufort force description, letting you compare it directly against instrument readings or other weather sources. Converting a measured wind speed to Beaufort Number gives you the equivalent force rating, which may fall between whole numbers, useful for understanding exactly how close current conditions are to the next Beaufort threshold (and its associated sea-state or safety warnings).

Because the Beaufort scale is non-linear, the converted values highlight how each additional force number represents an increasingly large jump in actual wind speed, especially at the higher (storm and hurricane) end of the scale.

How to use this Beaufort Scale calculator

  1. Select your starting unit from the From dropdown, Beaufort Number, or one of the speed units (km/h, mph, m/s, Knots).
  2. Enter your value, such as 6 for a Beaufort force 6 reading.
  3. Select your target unit from the To dropdown, such as km/h.
  4. Read the converted result, which updates instantly.
  5. Use the swap (⇅) button to convert a known wind speed back into its Beaufort equivalent.
  6. Cross-check the result against a Beaufort scale description table if you need the associated sea-state or land-effect terminology (e.g. "Fresh Breeze," "Gale").

Formula & Methodology

All conversions route through wind speed in metres per second (m/s) as the canonical unit, using the World Meteorological Organization's standard empirical Beaufort formula:

V (m/s) = 0.836 × B^1.5  |  B = (V ÷ 0.836)^(2/3)

Worked example: Converting Beaufort force 8 to km/h, V = 0.836 × 8^1.5 = 0.836 × 22.627 ≈ 18.9 m/s. Converting m/s to km/h: 18.9 ÷ 0.277778 ≈ 68.1 km/h, matching the commonly cited wind speed range for Beaufort force 8 ("Fresh Gale," roughly 62-74 km/h).

Frequently Asked Questions

The Beaufort scale is a system for estimating wind strength using numbers from 0 (calm) to 12 (hurricane force), originally developed for sailors to judge wind conditions from observed effects on the sea's surface or on land, such as smoke drift, tree movement, or wave height. It's still used today in shipping forecasts and marine weather reports alongside numeric wind speed.
The World Meteorological Organization's standard empirical formula is V (m/s) = 0.836 × B^1.5, where B is the Beaufort number. This converter applies that exact formula, so a Beaufort force of 6 converts to approximately 12.3 m/s, or about 44.3 km/h.
Beaufort force 5 ('Fresh Breeze') corresponds to approximately 10.5 m/s, or roughly 37.7 km/h / 23.4 mph / 20.4 knots, using the standard Beaufort formula. At this force, small trees begin to sway and small waves form white crests on open water.
Select Beaufort Number (0-12) as your From unit, enter the force number, then select km/h, mph, or Knots as your To unit. The tool calculates the equivalent wind speed instantly using the standard meteorological formula.
Select your speed unit (km/h, mph, m/s, or Knots) as the From unit, enter the wind speed, and select Beaufort Number as the To unit. The tool inverts the standard formula to give you the equivalent Beaufort force, which may be a decimal value between whole force numbers.
Beaufort force 10 is classified as 'Storm,' force 11 as 'Violent Storm,' and force 12 is 'Hurricane force,' corresponding to sustained wind speeds above roughly 32.7 m/s (about 118 km/h) at force 12. This aligns with the wind speed threshold used to define a Category 1 hurricane on the Saffir-Simpson scale.
The Beaufort scale remains useful because it links a simple number directly to observable, real-world effects (calm smoke, swaying trees, high waves), making it easy to communicate and visually estimate wind conditions without an anemometer, especially at sea. Marine forecasts and shipping bulletins still report wind force in Beaufort numbers alongside or instead of raw speed figures.
No, the Beaufort scale is non-linear, following a power-law relationship (speed proportional to B^1.5) rather than increasing by a constant speed increment per force number. This means the speed difference between Beaufort 1 and 2 is much smaller than the speed difference between Beaufort 11 and 12.
Beaufort force 0 is defined as 'Calm,' with wind speeds under about 0.5 m/s (roughly 1 km/h), where smoke rises vertically and the sea surface is mirror-like. This converter returns a Beaufort value of 0 for any wind speed at or near this threshold.
Yes, the Beaufort scale remains standard in marine shipping forecasts, coastal weather warnings, and some aviation weather briefings worldwide, particularly for describing sea state and small-craft wind warnings. This converter is useful for translating between the numeric wind speed used in general weather apps and the Beaufort force referenced in marine forecasts.
Also known as
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