Tornado Enhanced Fujita Scale Wind Speed Estimator
Look up EF tornado scale wind speeds, damage descriptions, and frequencies for any EF0 to EF5 tornado rating.
Calculate dynamic pressure and energy comparisons.
The history: from Fujita to Enhanced Fujita
Tetsuya “Ted” Fujita developed the original F-scale in 1971 at the University of Chicago, working with Allen Pearson of the National Severe Storms Forecast Center. His scale ranged from F0 (40-72 mph) to F5 (261-318 mph) and was based on observed damage with theoretical wind speeds attached. The scale revolutionized tornado climatology.
But Fujita’s original wind speeds were always controversial. They had been estimated from limited data and tended to overstate wind speeds at the high end. The May 3, 1999 Bridge Creek-Moore Oklahoma tornado was particularly important: a Doppler radar measured wind speeds of 318 mph at about 100 ft above ground level (the highest wind ever measured on Earth), confirming that even F5-level damage occurred at lower wind speeds than Fujita assumed.
The Enhanced Fujita (EF) Scale replaced the original F-scale in the United States on February 1, 2007. The major changes:
- Lower wind speed thresholds (more realistic engineering analysis)
- Damage Indicators (28 building types and tree categories)
- Degrees of Damage (gradient within each indicator)
- More structured, repeatable assessment process
The EF scale is not used internationally — Canada adopted it in 2013, but most countries (UK, Australia, Japan, Europe) use the original F-scale or their own national scales.
EF wind speed ranges (3-second gust at the ground)
| Rating | Wind speed (mph) | Wind speed (km/h) | Frequency in US |
|---|---|---|---|
| EF0 | 65-85 | 105-137 | ~53% |
| EF1 | 86-110 | 138-177 | ~32% |
| EF2 | 111-135 | 178-217 | ~11% |
| EF3 | 136-165 | 218-266 | ~3% |
| EF4 | 166-200 | 267-322 | ~1% |
| EF5 | > 200 | > 322 | < 0.1% (~1 per year avg) |
Total US tornadoes per year average around 1,200. So in a typical year:
- ~640 EF0 (weak, usually brief)
- ~380 EF1 (moderate damage)
- ~130 EF2 (considerable damage)
- ~36 EF3 (severe)
- ~12 EF4 (devastating)
- ~1 EF5 (incredible, complete destruction)
Damage descriptions — what each level looks like
EF0 (65-85 mph): Small tree branches broken. Shallow-rooted trees pushed over. Minor roof damage (shingles, gutters). Most house construction undamaged.
EF1 (86-110 mph): Roof shingles severely stripped. Mobile homes (unsupported) overturned or severely damaged. Outbuildings and unattached garages demolished. Trees snapped.
EF2 (111-135 mph): Roofs torn from well-constructed homes. Mobile homes destroyed. Foundations of frame homes shifted. Large trees uprooted. Cars lifted from the ground.
EF3 (136-165 mph): Entire stories of well-constructed houses destroyed. Most/all walls of weaker construction collapsed. Trees debarked. Trains overturned. Heavy cars thrown.
EF4 (166-200 mph): Well-constructed houses leveled. Foundations may be swept clean. Cars thrown long distances. Steel-reinforced concrete structures badly damaged.
EF5 (>200 mph): Strong frame houses swept away. Even foundations damaged. Steel-reinforced concrete structures critically damaged. Automobile-sized projectiles thrown 100+ meters. Trees stripped of all bark and small branches.
The “EF5 problem” — why this rating is so rare
EF5 ratings have always been controversial. To rate an EF5, surveyors need to find a structure that was:
- Well-constructed enough that EF4 winds (166-200 mph) wouldn’t have leveled it
- Hit directly by the tornado’s strongest winds
- Completely swept away from its foundation, with foundation damage
This combination is rare. Many likely-EF5 tornadoes get rated EF4 because there wasn’t a strong enough structure in the path to provide unambiguous evidence. Some experts argue the El Reno, OK 2013 tornado (radar-measured 295+ mph winds) should have been EF5, but was rated EF3 because it stayed mostly over rural farmland.
Recent EF5s in the United States:
- May 4, 2007: Greensburg, KS (entire town destroyed)
- May 25, 2008: Parkersburg, IA
- April 27, 2011: Smithville, MS; Hackleburg, AL; Philadelphia, MS; Rainsville, AL (four EF5s in one day during the super outbreak)
- May 22, 2011: Joplin, MO (158 killed)
- May 24, 2011: El Reno, OK
- May 20, 2013: Moore, OK
The last EF5 in the US was May 20, 2013. As of late 2024, an 11-year EF5 drought continues — the longest in modern record-keeping. Reasons debated: improved building codes raising the damage threshold; possible undermining by current EF5 assessment methodology.
Dynamic pressure — what wind does to structures
A 200 mph wind exerts a dynamic pressure of:
q = 0.5 × ρ × v² q = 0.5 × 1.225 kg/m³ × (200 × 0.447)² m²/s² q = 0.5 × 1.225 × 8000 q = 4,900 Pa = 102 lb/ft²
That’s pressure equivalent to about 7 inches of water. On a single 8-foot × 16-foot wall (128 sq ft), the total wind force is about 13,000 lbf — enough to lift a small car.
| Wind speed | Dynamic pressure | Comparable to |
|---|---|---|
| 65 mph (EF0 low) | ~14 lb/ft² | Standard wind design load |
| 110 mph (EF1 high) | ~31 lb/ft² | Hurricane Category 3 |
| 165 mph (EF3 high) | ~70 lb/ft² | Hurricane Category 5 |
| 200 mph (EF4 high) | ~102 lb/ft² | EF5 threshold |
| 250 mph (EF5 violent) | ~160 lb/ft² | Most concrete structures fail |
| 318 mph (Bridge Creek 1999) | ~258 lb/ft² | Highest wind ever measured |
Standard residential construction is designed for about 90 mph winds (~22 lb/ft² dynamic pressure). At EF3 wind speeds, the loads exceed design capacity by 3x. At EF5, by 8-10x. This is why “shelter in place” usually fails for EF4+ tornadoes — only a basement, storm shelter, or specially-built safe room provides reliable protection.
Tornado climatology — where and when
The US averages ~1,200 tornadoes per year, but they’re highly concentrated:
Geographic distribution:
- Tornado Alley (TX/OK/KS/NE/SD): peak May-June, classic supercells
- Dixie Alley (MS/AL/TN/LA): peak March-May and November, more violent ratings, more nighttime tornadoes, more deadly
- Carolina/FL Panhandle: peak hurricane-spawned and cool-season
- Upper Midwest (IA/MN/WI): peak June-July
- Western Rockies: very rare
- Northeast US: occasional but rare
Seasonal distribution:
- March-May: peak season for southern plains
- May-June: peak for central plains
- June-July: peak for northern plains
- Late fall (Oct-Nov): secondary peak in Dixie Alley
- Winter: rare but possible in deep south
Time of day: 60-70% of tornadoes occur between 3 PM and 9 PM local time. But Dixie Alley has a much higher percentage of nighttime tornadoes — which are far more deadly because people are asleep and can’t see the warning signs.
Tornado safety
When a tornado warning is issued for your area:
- Best: underground storm shelter, basement, or below-ground safe room (concrete and steel reinforced)
- Acceptable: interior bathroom or closet on lowest floor, away from windows
- Avoid: mobile homes (overturned in EF1 winds), large open rooms, vehicles (impossible to outrun a tornado in traffic)
- Worst: overpass (wind tunnel effect actually increases wind speed)
Buy a NOAA weather radio. Have a plan before storms hit. Practice with your family. The lead time on tornado warnings averages 13 minutes — enough to shelter if you act immediately.
Bottom line
The Enhanced Fujita scale (EF0-EF5, since 2007) rates tornadoes by damage with wind speed estimates from engineering analysis. EF0-EF1 represent 85% of all tornadoes; EF5 events are extraordinarily rare (~1 per year, with an 11-year drought from 2013-2024). Modern radar can measure tornado winds directly but the EF scale remains the operational standard. For tornado warnings, the only safe options are underground or a structurally-engineered safe room — interior bathrooms can save lives in EF0-EF2 events but not in violent tornadoes.