OceanCalc

Beaufort Scale Calculator

Enter wind speed in knots, mph, km/h, or m/s to get the corresponding Beaufort force and sea state description.

Last updated: March 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.

Overview

The Beaufort Scale Calculator gives you precise nautical results from familiar formulas, with an interface suited to deck and chart-table use.

How to use

With the Beaufort Scale Calculator, type your figures into the inputs above—the output refreshes live, making it easy to sanity-check several cases.

Formula

The relationship behind this tool is: 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

Typical uses for the Beaufort Scale Calculator include passage planning, briefing crew, converting instrument readouts to chart units, and double-checking mental math when fatigue or weather make errors more likely.

Tips for accuracy

  • Confirm that the units you enter match your chart, GPS, or instrument readout before relying on the Beaufort Scale Calculator.
  • In rough weather or poor visibility, cross-check important results with a second method or a crew member.
  • Treat simplified models (wave height, radar horizon, etc.) as estimates—real conditions vary with fetch, refraction, and equipment.

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?

    This calculator uses standard maritime formulas and practical approximations where noted. It is suitable for planning and cross-checks; always verify safety-critical decisions with official references and local conditions.

  • Can I use this on mobile?

    Yes. OceanCalc tools are responsive and work on phones and tablets for quick checks on deck or in the cockpit.

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Results are estimates for educational purposes only and should not be used for real navigation decisions.

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