Enhanced Fujita Scale Calculator

Convert an estimated tornado wind speed in mph, km/h or m/s to an EF rating, compare it with the original Fujita scale, and look up the wind range for any EF level.

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EF scale wind ranges

The National Weather Service began rating tornadoes with the Enhanced Fujita scale on February 1, 2007. Its speeds are estimated 3-second gusts at the point of damage, in whole miles per hour:

EF065-85 mph
EF186-110 mph
EF2111-135 mph
EF3136-165 mph
EF4166-200 mph
EF5over 200 mph

Because the ranges use whole numbers, this calculator rounds to the nearest mph first: 85.4 mph is EF0 and 85.6 mph is EF1. Gusts below 65 mph get a below-EF0 message, though 58 mph already meets the NWS severe thunderstorm wind criterion.

Converting km/h and m/s

The calculator converts to mph with 1 m/s = 2.23694 mph and 1 km/h = 0.621371 mph, then classifies. A 50 m/s gust is 111.8 mph, which rounds to 112 mph and rates EF2. A 250 km/h gust is 155.3 mph, an EF3.

Watch the boundaries: 322 km/h is 200.08 mph and still rates EF4, while 90 m/s is 201.3 mph and crosses into EF5. Radar-measured winds aloft are often higher than the damage-based EF estimate, which is one reason a tornado's rating can look low next to a Doppler on Wheels reading.

How the original Fujita scale compares

Ted Fujita's 1971 F-scale used fastest quarter-mile wind speeds. The Storm Prediction Center table lists F0 40-72, F1 73-112, F2 113-157, F3 158-207, F4 208-260 and F5 261-318 mph. Engineers later concluded those upper speeds were too high for the damage they described, so the EF scale lowers them.

  • The same numeric speed maps to a different level on each scale. 150 mph is an EF3 but only an F2.
  • Compare ratings by damage, not by speed. An old F3 and a new EF3 describe similar destruction.
  • Ratings issued before 2007 were not re-rated, so historical F ratings stay on the old scale in NOAA's records.

Winds are inferred from damage indicators

Nobody measures an EF rating with an anemometer. Survey teams match what they see to 28 damage indicators, each with a set of degrees of damage and an expected wind speed. Examples include DI 1 small barns and farm outbuildings, DI 2 one- or two-family residences, DI 3 single-wide mobile homes, DI 15 one-story elementary schools, DI 24 transmission line towers, and DI 27 and 28 hardwood and softwood trees.

The rating reflects the most intense damage found, not the average. A tornado that crosses only open fields can be rated EF0 or left unrated even if its winds were violent, because there was nothing to damage. Single-wide mobile homes (DI 3) fail at much lower speeds than well-built houses (DI 2), so surveyors pay closest attention to the strongest structures that were destroyed.

Frequently Asked Questions

Common questions about the Enhanced Fujita Scale Calculator

An EF5 has estimated 3-second gusts over 200 mph. 200 mph itself is still EF4, and 201 mph is EF5.

Sources & References

Enhanced F Scale for Tornado Damage

Official EF scale wind ranges, the F-scale comparison table and the 28 damage indicators.
→Source: NOAA Storm Prediction Center

Enhanced F Scale table and damage indicators

Fujita, derived EF and operational EF wind ranges side by side.
→Source: NOAA Storm Prediction Center

Tornado FAQ

Background on tornado ratings, damage surveys and records.
→Source: NOAA Storm Prediction Center

Tornado Safety

NWS guidance on tornado watches, warnings and sheltering.
→Source: National Weather Service

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