This table gives approximate asteroid diameters as a function of absolute magnitude (H) and surface albedo (reflectivity). Values are estimates based on standard asteroid photometric relationships.
Lower H values correspond to intrinsically brighter and generally larger asteroids, while darker surfaces (lower albedo) imply larger physical sizes for the same H value.
| H | 0.30 | 0.25 | 0.20 | 0.15 | 0.10 | 0.05 |
|---|---|---|---|---|---|---|
| 34 | 0.38 m | 0.42 m | 0.47 m | 0.54 m | 0.67 m | 0.94 m |
| 33 | 0.61 m | 0.67 m | 0.75 m | 0.86 m | 1.1 m | 1.5 m |
| 32 | 0.97 m | 1.1 m | 1.2 m | 1.4 m | 1.7 m | 2.4 m |
| 30 | 2.5 m | 2.7 m | 3.0 m | 3.5 m | 4.3 m | 6.0 m |
| 28 | 6.2 m | 6.8 m | 7.6 m | 8.7 m | 11 m | 15 m |
| 26 | 16 m | 17 m | 19 m | 22 m | 27 m | 38 m |
| 24 | 39 m | 43 m | 48 m | 55 m | 68 m | 96 m |
| 22 | 98 m | 110 m | 120 m | 140 m | 170 m | 240 m |
| 20 | 160 m | 270 m | 300 m | 350 m | 430 m | 600 m |
| 18 | 620 m | 680 m | 760 m | 870 m | 1.1 km | 1.5 km |
| 16 | 1.6 km | 1.7 km | 1.9 km | 2.2 km | 2.7 km | 3.8 km |
| 14 | 3.9 km | 4.3 km | 4.8 km | 5.5 km | 6.8 km | 9.6 km |
| 12 | 9.8 km | 11 km | 12 km | 14 km | 17 km | 24 km |
| 10 | 25 km | 27 km | 30 km | 35 km | 43 km | 60 km |
These values are approximate. Actual asteroid sizes depend on shape, composition, rotation, and surface properties. Where possible, radar and thermal observations provide more precise measurements.
Formula used:Note: d is in kilometers.
Absolute Magnitude (H)The brightness an asteroid would appear to have if it were positioned 1 astronomical unit from both the Sun and the Earth and observed at zero phase angle.
Albedo (a) Definition:The fraction of sunlight that an object reflects back into space.
Explanation:Albedo ranges between two physical extremes from 0 (completely dark, reflecting no sunlight) to 1 (perfectly reflective, returning all sunlight). The Moon's average albedo is about 0.12.
Sources: E. Bowell et al. (1989), Asteroids II; A. Harris & A. Harris (1997), Icarus 126:450–454; NASA CNEOS, Asteroid Size Estimator tool; Conversion of Absolute Magnitude to Diameter (The Minor Planet Center).
These comparisons help visualize estimated asteroid diameters. Values are approximate and meant for intuition.
| Approx. size | Reference object |
|---|---|
| 0.5 m | Large suitcase |
| 1 m | Dining table |
| 2 m | Compact car |
| 5 m | SUV / pickup truck |
| 10 m | City bus |
| 15 m | Two buses |
| 20 m | Tractor-Trailer With a Cab |
| 30 m | Jetliner fuselage length |
| 50 m | Half a football field |
| 100 m | Football field |
| 150 m | Great Pyramid height |
| 200 m | Two football fields |
| 300 m | Eiffel Tower height |
| 500 m | Empire State Building height |
| 1 km | Golden Gate Bridge main span |
| 5 km | Bolte Bridge in Docklands, Australia |
| 10 km | Paris (Central City) |