Hurricane category calculator
Turn a wind speed into its Saffir-Simpson hurricane category and its Beaufort force, from the US National Hurricane Center's and NOAA's own tables. Enter the storm's maximum sustained wind, in km/h, mph, knots or metres a second.
Saffir-Simpson (example)
Category 2
Category 2 hurricane
NHC: Extremely dangerous winds will cause extensive damage.
Beaufort force 12: Hurricane (64 knots or more)
160 km/h · 99 mph · 86 knots · 44.4 m/s
The Saffir-Simpson hurricane wind scale
| Category | Knots | mph | km/h | NHC |
|---|---|---|---|---|
| Category 1 | 64-82 | 74-95 | 119-153 | Very dangerous winds will produce some damage. |
| Category 2 | 83-95 | 96-110 | 154-177 | Extremely dangerous winds will cause extensive damage. |
| Category 3 | 96-112 | 111-129 | 178-208 | Devastating damage will occur. A major hurricane. |
| Category 4 | 113-136 | 130-156 | 209-251 | Catastrophic damage will occur. A major hurricane. |
| Category 5 | 137 or higher | 157 or higher | 252 or higher | Catastrophic damage will occur. A major hurricane. |
From the National Hurricane Center. Category 3 and higher are major hurricanes. Below 64 knots: tropical storm 34-63 knots (39-73 mph, 63-118 km/h), tropical depression 33 knots (38 mph, 62 km/h) or less. "Sustained wind" here is the highest one-minute average wind at 10 metres. The scale rates wind only: the NHC notes it does not account for storm surge, rainfall flooding or tornadoes.
The Beaufort wind scale
| Force | Description | Knots | About km/h |
|---|---|---|---|
| 0 | Calm | under 1 | under 2 |
| 1 | Light air | 1-3 | 2-6 |
| 2 | Light breeze | 4-6 | 7-11 |
| 3 | Gentle breeze | 7-10 | 13-19 |
| 4 | Moderate breeze | 11-16 | 20-30 |
| 5 | Fresh breeze | 17-21 | 31-39 |
| 6 | Strong breeze | 22-27 | 41-50 |
| 7 | Near gale | 28-33 | 52-61 |
| 8 | Gale | 34-40 | 63-74 |
| 9 | Strong gale | 41-47 | 76-87 |
| 10 | Storm | 48-55 | 89-102 |
| 11 | Violent storm | 56-63 | 104-117 |
| 12 | Hurricane | 64+ | 119+ |
Knots and descriptions from NOAA's Storm Prediction Center (WMO classification). The km/h column is converted here (1 knot = 1.852 km/h) and rounded.
How it is calculated
The speed you enter is rounded to a whole number in its own unit and looked up in the NHC table for that unit, because the NHC publishes the scale in whole knots, mph and km/h. The NHC gives no table in metres a second, so m/s is turned into knots first (1 knot = 1852 m per hour = 0.5144 m/s). The Beaufort force is read from the speed in knots, rounded to a whole knot.
knots = km/h ÷ 1.852 knots = mph ÷ 1.15078 knots = m/s ÷ 0.514444
Worked example: 160 km/h
160 km/h is in the NHC Category 2 range (154-177 km/h) → Category 2 160 ÷ 1.852 = 86.4 knots → Beaufort force 12 (Hurricane, 64 knots or more)
Typhoons and cyclones in other oceans
The Saffir-Simpson scale is the US National Hurricane Center's scale for the Atlantic and eastern North Pacific. Elsewhere, tropical cyclones are named and rated by the regional warning centres, on their own scales and often with a different averaging time for the wind: for example the India Meteorological Department in the north Indian Ocean, the Japan Meteorological Agency in the western North Pacific, and Australia's Bureau of Meteorology around Australia. Their categories are not the same as Saffir-Simpson categories, so this calculator does not convert to them; read the category from the agency that issued it.
This calculator gives an estimate for learning and planning. It is not a forecast or a warning, and it cannot say whether conditions are safe. For decisions, follow your national weather service and local authorities.
Sources
- National Hurricane Center: Saffir-Simpson Hurricane Wind Scale: category ranges in knots, mph and km/h, damage wording, major hurricanes
- National Hurricane Center: Glossary: tropical depression, tropical storm, hurricane, and "maximum sustained surface wind"
- NOAA Storm Prediction Center: Beaufort Wind Scale: forces 0-12 in knots with WMO descriptions
Questions
What wind speed is a Category 5 hurricane?
On the US Saffir-Simpson scale, Category 5 is a 1-minute sustained wind of 137 knots or more, which the National Hurricane Center gives as 157 mph or 252 km/h or higher. Category 3 and above are major hurricanes.
Is a typhoon or cyclone measured on the same scale?
Not officially. The Saffir-Simpson scale is the scale of the US National Hurricane Center. Other regions are rated by their own warning centres on their own scales, for example the India Meteorological Department, the Japan Meteorological Agency and Australia's Bureau of Meteorology, and they do not all average the wind over the same length of time.
What does the Saffir-Simpson category leave out?
The scale is based only on wind speed. The National Hurricane Center notes it does not account for storm surge, rainfall flooding or tornadoes, which often cause more harm than the wind.