What is the Saffir-Simpson Hurricane Scale?
The Saffir-Simpson Hurricane Wind Scale is a 1-to-5 rating used by the U.S. National Hurricane Center to classify hurricanes based on their maximum sustained wind speed. Higher categories indicate stronger winds and the potential for greater property damage. This calculator takes a sustained wind speed and tells you exactly which category a storm falls into, with conversions between mph, knots and km/h.
How to use this calculator
Enter the maximum sustained (1-minute) wind speed of the storm and choose the unit you measured it in — miles per hour, knots, or kilometers per hour. The calculator converts your value to mph, applies the Saffir-Simpson thresholds, and returns the category along with the equivalent speed in all three units.
$$\text{Category} = f\!\left(V_{\text{mph}}\right), \quad V_{\text{mph}} = \text{Wind (mph)}$$
$$\text{Category} = \begin{cases} \text{TS} & 39 \le V_{\text{mph}} < 74 \\ 1 & 74 \le V_{\text{mph}} \le 95 \\ 2 & 96 \le V_{\text{mph}} \le 110 \\ 3 & 111 \le V_{\text{mph}} \le 129 \\ 4 & 130 \le V_{\text{mph}} \le 156 \\ 5 & V_{\text{mph}} \ge 157 \end{cases}$$
$$V_{\text{mph}} = \text{Wind (kt)} \times 1.15078$$
$$V_{\text{mph}} = \frac{\text{Wind (km/h)}}{1.609344}$$
The category thresholds
In miles per hour the boundaries are: Category 1 = 74-95, Category 2 = 96-110, Category 3 = 111-129, Category 4 = 130-156, and Category 5 = 157 or higher. Categories 3, 4 and 5 are classed as "major" hurricanes. Winds below 74 mph are a tropical storm (39-73 mph) or tropical depression (under 39 mph) and are not hurricanes.
Worked example
Suppose a storm has sustained winds of 120 mph. Because \(111 \le 120 \le 129\), it falls into the Category 3 band, making it a major hurricane. In other units that is about 104.3 knots or 193.1 km/h.
FAQ
Does the scale account for storm surge or rainfall? No. The modern Saffir-Simpson scale is based on wind speed only. Flooding from storm surge and rain can be devastating even in lower-category storms.
Which wind speed should I use? Use the maximum 1-minute sustained wind speed, not gusts. Wind gusts are typically higher than the sustained value.
Is there a Category 6? No. The scale stops at Category 5, which is open-ended (157 mph and above), so the most intense storms remain Category 5.
