About the Beaufort Scale
This calculator translates a Beaufort wind force number (0 through 12) into its corresponding wind speed range and the classic observable description, from "Calm" to "Hurricane force." It's aimed at sailors, weather enthusiasts, and anyone trying to make sense of a Beaufort reading mentioned in a forecast or historical account.
How It Works
Enter a whole number from 0 to 12, and the calculator looks up that force's wind speed range in both mph and km/h along with its standard descriptive name. Values outside 0-12 are pulled back to the nearest valid endpoint, and non-whole numbers are rounded before the lookup.
Examples
Fresh breeze at sea
Force 5 corresponds to a wind speed of 19-24 mph (about 31-39 km/h) and is described as a "Fresh breeze," a level where small trees begin to sway.
Gale-force winds
Force 8 corresponds to 39-46 mph (about 63-74 km/h) and is described as a "Gale," strong enough to break twigs off trees and generally impede walking.
Advantages
- Converts a Beaufort number directly into both mph and km/h ranges, avoiding the need to separately look up and convert wind speed units.
- Pairs the numeric wind speed with the traditional descriptive name, which is often more meaningful in a forecast or logbook context than a raw number.
- Automatically handles out-of-range or non-whole-number input by clamping and rounding to the nearest valid Beaufort force.
Common Mistakes
- Treating each Beaufort force as a single exact wind speed rather than a range, when the scale was designed around bands of observable effects.
- Assuming the scale is linear, when the wind speed range covered by each step actually widens at higher force numbers rather than staying constant.
- Forgetting that Beaufort force was originally an observational scale based on visible effects like sea state or swaying trees, not a direct anemometer reading, so real-world estimates can vary.
Edge Cases to Watch For
- Any input above 12 is treated as force 12 ("Hurricane force," shown with an upper wind speed bound of 73-999 mph), since the Beaufort scale has no higher defined step.
- Any input below 0 is treated as force 0 ("Calm"), and decimal inputs are rounded to the nearest whole force number before lookup, since the scale only defines integer steps.
- Each force level maps to a wind speed range rather than a single value, reflecting how the original scale was built around observable ranges of effect rather than precise instrument readings.
Common Use Cases
- Sailors and boaters interpreting a marine forecast's Beaufort number in terms of practical wind speed for sail planning.
- Weather hobbyists and students studying historical or international forecasts that still reference the Beaufort scale.
- Readers of older maritime logs, novels, or reports translating a Beaufort force mention into a modern wind speed figure.