Beaufort number to wind speed range
Turn a Beaufort force into the speed band forecasts mean: force 6 is a strong breeze of 22 to 27 knots, or 10.8 to 13.8 m/s. You get the published range, not a single estimated speed. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Force
- 6
- Force name
- Strong breeze
- Knots min
- 22
- Meters per second min
- 10.8
- Knots range
- 22–27 kn
The Beaufort force number is still the language of marine forecasts, coastal radio, and many classroom weather labs: force four is a moderate breeze, force eight is a gale, and force twelve is hurricane force. This Beaufort number to wind speed range calculator accepts an integer force from zero through twelve and returns the official World Meteorological Organization mean-wind band in knots and in metres per second, together with the conventional force name. Unlike a continuous converter that maps a force to one speed with an empirical power formula, this landing reports the discrete published range that synoptic tables actually list.
What a Beaufort force number means as a wind-speed range
Sir Francis Beaufort’s nineteenth-century scale ranks wind by what it does to the sea and to objects on land, not by a single anemometer reading. Operational meteorology later attached a mean-wind interval to each integer force from calm through hurricane force so that a radio bulletin saying force six always meant the same band of speed. This calculator looks up those official World Meteorological Organization bands.
Force zero is calm: less than one knot, or zero point zero through zero point two metres per second. Force one through three cover light air, light breeze, and gentle breeze, from one to ten knots and from zero point three through five point four metres per second. Force four through six are moderate, fresh, and strong breeze, eleven through twenty-seven knots.
Force seven through nine are near gale, gale, and strong gale, twenty-eight through forty-seven knots. Force ten and eleven are storm and violent storm, forty-eight through sixty-three knots. Each row is a closed or half-open interval of mean wind, not a point estimate.
Here force six is always twenty-two to twenty-seven knots and ten point eight to thirteen point eight metres per second, matching the table skippers, examiners, and coastal bulletins actually quote when they translate a force number into instrument units.
What you can do with it
Sailing school and exam answers
Return the official knot and metre-per-second bands for a set Beaufort force so weather-theory items can be marked against the published table.
Forecast force to instrument units
Translate a coastal or routing forecast that quotes force eight into the matching 34–40 kn and 17.2–20.7 m/s bands for crew briefings.
Logbook and notice templates
Fill marina notices and electronic logs from an integer force with a stable force name plus both official speed ranges.
FAQ
How do I convert a Beaufort number into a wind speed range?
Send force as an integer from 0 to 12.
Which units does the Beaufort number to wind speed range calculator return?
Always both knots (kn) and metres per second (m/s), as published on the operational WMO 0–12 mean-wind table. It does not convert to mph or km/h.
Why does force 12 have no upper speed bound?
Hurricane force on the operational 0–12 scale is an open-ended tail: 64 kn and above, or 32.7 m/s and above.
What happens if the Beaufort number is outside zero to twelve?
Negative forces, fractions, and integers above twelve (including extended classes 13–17) are rejected and are not billed.
What wind speed is a force 8 gale?
A force 8 gale means mean winds of 34 to 40 knots, or 17.2 to 20.7 metres per second. Use that band when a coastal or routing forecast announces force eight and the crew needs instrument units.
Related tools
For developers — API access
Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.
API endpoint
Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.
Call it from your stack
curl -X POST https://api.kit.forhosting.com/earth/beaufort-to-wind-speed \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"force":6}'const res = await fetch("https://api.kit.forhosting.com/earth/beaufort-to-wind-speed", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"force": 6
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/earth/beaufort-to-wind-speed",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"force": 6
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/earth/beaufort-to-wind-speed", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"force":6}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"force":6}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/earth/beaufort-to-wind-speed", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"force": 6
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "earth.beaufort_to_wind_speed",
"status": "queued",
"_links": {
"result": "/tasks/tsk_…/result"
}
}The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.
Pricing
Published price — no tokens, no invented credits. A failed task is never charged.
Errors
| HTTP | Code | Meaning |
|---|---|---|
401 | unauthorized | Missing or invalid API key. |
402 | insufficient_balance | Your balance doesn't cover the task price. |
404 | unknown_type | That task type doesn't exist. |
429 | rate_limited | Too many requests. Use the webhook instead of polling. |
Technical notes
Force numbers outside the closed operational scale of zero to twelve fail with invalid_input and are not billed.
What a Beaufort force number means as a wind-speed range
Force twelve is hurricane force: sixty-four knots and above, or thirty-two point seven metres per second and above, with no published upper bound on the operational zero-to-twelve scale. A continuous formula such as zero point eight three six times force to the three-halves power is useful when you need one representative speed; it is not what this endpoint returns.
Input contract, response fields, and out-of-scale errors
Integers below zero or above twelve are rejected with a message that the Beaufort number is outside zero to twelve, because the operational WMO scale used here does not invent extended classes thirteen through seventeen. Those failures are not billed. Example: force six yields Strong breeze, twenty-two to twenty-seven knots, and ten point eight to thirteen point eight metres per second. POST a JSON object with force, a required integer Beaufort number from zero through twelve inclusive. Aliases beaufort, beaufort_number, bft, and b are accepted and mean the same field. The value may arrive as a JSON integer or as a whole-number string; fractional values such as six point five, non-numeric text, missing fields, empty strings, and non-finite numbers fail with invalid_input naming force. On success the body echoes force, returns force_name such as Strong breeze, and reports knots_min, knots_max, meters_per_second_min, and meters_per_second_max as the inclusive published bounds. For force twelve the upper bounds are omitted and unbounded is true, because hurricane force is an open-ended tail on this scale. knots_range and meters_per_second_range are short display strings such as twenty-two to twenty-seven kn. scale names the WMO Beaufort zero-to-twelve mean-wind table, and description combines force, name, and both ranges for a log line. Pair this lookup with your own instrument feed if you need gust peaks or a continuous mid-band speed; this endpoint reports official mean-wind ranges only. Successful analytic calls use the published $0.002 base price with no model tokens and no outbound network.
Where a force-to-range Beaufort API earns its keep
Sailing schools and weather-theory exams ask what wind speed Beaufort six represents and expect the published knot and metre-per-second bands, not a single converted number from a power formula. Electronic logbooks and marina notices often start from a forecast force, not from an anemometer: they need the matching knot band so a force-eight expected briefing can also show thirty-four to forty knots for crews who think in instrument units. Research and content pipelines that batch every force from zero through twelve need fixed table values they can pin in tests, including the unbounded hurricane-force tail. A deterministic range API lets a lesson page or an auto-grader mark the official interval and reject force thirteen as out of scale instead of quietly mapping it to an extended hurricane class. Send an integer force on the closed scale, pin knots_min and meters_per_second_min in tests, and you get reproducible official ranges for courses, docs, and edge workers without standing up a meteorology library of your own.
Technical questions
What does the Beaufort number to wind speed range calculator cost?
The browser tool is free. API requests use prepaid KIT balance at $0.002 per successful call; invalid input is not billed.