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A hectometre (American spelling: hectometer, symbol hm) is an uncommonly used unit of length in the metric system, equal to one hundred metres. It derives from the Greek word "ekato", meaning "hundred". A regulation football or soccer field is approximately 1 hectometre in length.
- For area the square hectometer (hm2) is a common unit. It is more commonly known by the name of hectare (ha), meaning 100 ares (100 a). The are is a measurement of area the size of 1 decametre by 1 decametre, which is 10 metres by 10 metres. Hence 100 ares equals an area with dimensions 100 m by 100 m — 1 hectometre by 1 hectometre, the square hectometre — equalling 10,000 square metres (10,000 m2)
- For volumes the cubic hectometre (hm3) is also used, 100 m by 100 m by 100 m equalling 1,000,000 cubic metres (1,000,000 m3).
Click on the thumbnail image to jump to the desired Human-scale order of length magnitude
article: top-left is 1E-6 m, lower-right is 1E5 m.
The Pyramid of Cheops is 138.8 metres high.
To compare different orders of magnitude this page lists lengths between 100 metres and 1000 metres (1 kilometre).
Distances shorter than 100 metres
100 metres (sometimes termed a hectometre) is equal to:
Human-defined scales and structures 
- 100 metres — wavelength of the highest mediumwave radio frequency, 3 MHz
- 100 metres — Spacing of location marker posts on British motorways.
- 138.8 metres — height of the Great Pyramid of Giza (Pyramid of Cheops)
- 139 metres — height of the world's tallest roller coaster, Kingda Ka
- 187 metres— shortest wavelength of the broadcast radio AM band, 1600 kHz
- 202 metres — length of the Széchenyi Chain Bridge connecting Buda and Pest
- 320.75 metres — height of the Eiffel Tower(including antenna) 
- 328 metres — height of Auckland's Sky Tower, the tallest free-standing structure in the Southern Hemisphere
- 341 metres — height of the world's tallest bridge, the Millau Viaduct
- 390 metres — height of the Empire State Building
- 400–800 metres — approximate heights of the world's tallest skyscrapers of the past 80 years.
- 458 metres — length of the Knock Nevis, the world's largest supertanker
- 555 metres — longest wavelength of the broadcast radio AM band, 540 kHz
- 630 metres — height of the KVLY-TV mast, second tallest structure in the world.
- 646 metres — height of the Warsaw radio mast, the world's tallest structure until its collapse in 1991.
- 828 metres — height of Burj Khalifa, world's tallest structure on 17 January 2009
- 1000 metres — wavelength of the lowest mediumwave radio frequency, 300 kHz
Distances longer than 1 kilometre