- Severe hail
- 1 inch (quarter) or larger
- Significant severe
- 2 inches (hen egg) or larger
- US record
- 8.0 in, Vivian, SD, July 23, 2010
What are the standard hail sizes in inches?
Weather observers compare hailstones to common objects. The Storm Prediction Center (SPC) publishes the official conversion table, and National Weather Service spotter guides add a few smaller and larger objects. SPC encourages measuring a stone with a ruler rather than estimating it.
| Object | Diameter (in) | Typical effect on roofs |
|---|---|---|
| Pea | 0.25 | No functional damage to roofing |
| Marble or mothball | 0.50 | No functional damage to sound roofs |
| Dime | 0.70 | Below published roofing damage thresholds |
| Penny | 0.75 | Below published roofing damage thresholds; may mark soft metals |
| Nickel | 0.88 | Below published roofing damage thresholds; may dent soft metals |
| Quarter | 1.00 | Damage threshold for 3-tab asphalt shingles; NWS severe threshold |
| Half dollar | 1.25 | Threshold for laminated (architectural) asphalt and cedar shingles |
| Walnut or ping pong ball | 1.50 | Threshold for medium cedar shakes, fiber-cement tile, clay tile and gray slate |
| Golf ball | 1.75 | Threshold for concrete tile and green slate |
| Hen egg | 2.00 | Above most residential thresholds; SPC "significant" severe hail |
| Tennis ball | 2.50 | Threshold for built-up gravel (flat) roofs |
| Baseball | 2.75 | Damage likely on nearly every roofing material |
| Tea cup | 3.00 | Damage likely on nearly every roofing material |
| Softball | 4.00 | Damage likely on nearly every roofing material |
| Grapefruit | 4.50 | Damage likely on nearly every roofing material |
| CD or DVD | 4.75 | Damage likely on nearly every roofing material |
Some charts online swap softball and grapefruit. The SPC table lists softball at 4.00 inches and grapefruit at 4.50 inches.
What size hail is considered severe?
Since January 5, 2010, the National Weather Service issues severe thunderstorm warnings for hail 1 inch in diameter or larger (quarter size). The previous criterion was 3/4 inch (penny size). The wind criterion of 58 mph did not change.
The Storm Prediction Center also tracks significant severe weather, which for hail means stones 2 inches (hen egg) or larger.
What is the largest hailstone ever recorded in the US?
The US record hailstone fell in Vivian, South Dakota, on July 23, 2010. It measured 8.0 inches in diameter and 18.62 inches in circumference and weighed 1.9375 pounds (1 lb 15 oz). A stone that fell in Aurora, Nebraska, in 2003 still holds the record for circumference, at 18.75 inches.
How should you measure hail after a storm?
- Measure the longest diameter of the largest stones with a ruler or calipers as soon as it is safe; hail melts quickly.
- Photograph stones next to a ruler or a coin for scale.
- Note the time and location. Ground reports to the National Weather Service help calibrate radar estimates.
- After the stones melt, dents in soft metals (gutters, downspouts, vents, AC fins) still record the size. See how to identify hail damage on a roof.
How do hail maps estimate size where nobody measured?
Hail maps such as Hail Pro's use radar. NOAA's Maximum Estimated Size of Hail (MESH) product estimates the largest hail diameter across the whole country from storm reflectivity, including places with no ground reports. It is an estimate, not a measurement; see what MESH hail size means.
Frequently asked questions
Is golf ball hail 1.75 inches?
Yes. On the Storm Prediction Center chart, golf ball hail is 1.75 inches in diameter.
What size is quarter-size hail?
Quarter-size hail is 1 inch in diameter, the National Weather Service threshold for severe hail.
Is softball or grapefruit hail bigger?
Grapefruit hail (4.50 inches) is bigger than softball hail (4.00 inches) on the official SPC chart.
What size hail damages a roof?
Around 1 inch for 3-tab asphalt shingles and 1.25 inches for laminated shingles in field studies, and larger for tile, slate and wood shakes. Older roofs can fail at smaller sizes. Details in what size hail damages a roof.
Sources
- NOAA Storm Prediction Center: hail size conversion table
- NWS Detroit: Spotter Reference Guide (2024)
- NWS: Wind and hail size estimates reference
- NWS Tampa Bay Observer (Winter 2009-10): 1 inch severe hail criterion
- NOAA Storm Prediction Center: about SPC (significant severe criteria)
- NOAA: record hailstone, Vivian, South Dakota (July 23, 2010)
- Marshall, Herzog, Morrison and Smith (Haag Engineering), Hail Damage Threshold Sizes for Common Roofing Materials, AMS 2002