Windspeed
Windspeed conversions
The Icelandic Meteorological Office uses the SI (Systeme Internationale d´Unites) unit metres per second (m/s) in windspeed measurements. Here you can convert between different units of windspeed. Type a number into a textbox below and then click outside it. Please note that Beaufort-values are between 0 and 12.
Beaufort-values corresponds to windspeed intervals. If a number is entered in the Beaufort-box, other boxes will display appropriate median values for that Beaufort-number, approximated to the nearest integer. If a number is entered in other boxes, the Beaufort-box will display the approximated Beaufort-value. This approximation inevitable leads to a slight inaccuracy in the calculations. The figure on the right loosely shows the relationship between m/s and a few Beaufort-values.
The prerequisites of the calculations above are:
- The equation: W = 0.836B3/2 where W is windspeed in m/s and B is value on the Beaufort-scale.
- 1 m/s = 3.6 km/h = 1.944 knots (2.237 miles per hour)
Below is a detailed table with comparison between Beaufort-values, average windspeed and the median for the average windspeed in m/s, km/h, and knots.
Top of pageWindspeed classification
To ease the understanding of the m/s measurement, the following table can be used.
| Windspeed IN m/s | Description |
|---|---|
| <5 | Very slow wind |
| 5-10 | Rather slow wind |
| 10-20 | Considerable wind, may lead to difficulties |
| 20-30 | Very windy, caution is advised |
| >30 | Extreme wind, dangerous |
Comparison with Beaufort-values
| Windforce* |
Average windspeed** |
Median of average windspeed |
|||||
| Beaufort | Name |
m/s |
km/h |
knots |
m/s |
km/h |
knots |
| 0 | Calm |
0-0,2 |
< 1 |
< 1 |
0,0 |
0,0 |
0,0 |
| 1 | Light air |
0.3-1.5 |
1-5 |
1-3 |
0.8 |
3.0 |
1.6 |
| 2 | Light breeze |
1.6-3.3 |
6-11 |
4-6 |
2.4 |
8.5 |
4.6 |
| 3 | Gentle breeze |
3.4-5.4 |
12-19 |
7-10 |
4.3 |
15.6 |
8.4 |
| 4 | Moderate breeze |
5.5-7.9 |
20-28 |
11-16 |
6.7 |
24.1 |
13.0 |
| 5 | Fresh breeze |
8.0-10.7 |
29-38 |
17-21 |
9.3 |
33.6 |
18.2 |
| 6 | Strong breeze |
10.8-13.8 |
39-49 |
22-27 |
12.3 |
44.2 |
23.9 |
| 7 | Near gale |
13.9-17.1 |
50-61 |
28-33 |
15.5 |
55.7 |
30.1 |
| 8 | Gale |
17.2-20.7 |
62-74 |
34-40 |
18.9 |
68.1 |
36.8 |
| 9 | Strong gale |
20.8-24.4 |
75-88 |
41-47 |
22.6 |
81.3 |
43.9 |
| 10 | Storm |
24.5-28.4 |
89-102 |
48-55 |
26.4 |
95.2 |
51.4 |
| 11 | Violent storm |
28.5-32.6 |
103-117 |
56-63 |
30.5 |
10.8 |
59.3 |
| 12 | Hurricane |
>= 32.7 |
>= 118 |
>= 64 |
... |
... |
... |
-
*Windforce measured in Beaufort-values is not an objective observation of windspeed, but rather a subjective one, based on the impact of the wind on the environment.
-
**This empirical relation between windforce, estimated on the Beaufort-scale, and the windspeed is based on the 10 minute average of the windspeed. In reality, windspeeds can vary a lot in that time. As a result, windgusts can not be measured with the Beaufort-scale. Windspeeds are now generally measured with anemometers, which continuously record the momentary windspeed, i.e. windgusts, that can vary a great deal from a 10 minute average windspeed and therefore bear no relations to the Beaufort-scale.
