Hecto- (symbol: h) is a decimal unit prefix in the metric system denoting a factor of one hundred. It was adopted as a multiplier in 1795, and comes from the Greek ἑκατόν hekaton, meaning "hundred". In 19th century English it was sometimes spelled hecato, in line with a puristic opinion by Thomas Young.[1][2] Its unit symbol as an SI prefix in the International System of Units (SI) is the lower case letter h.

It is rarely used except in certain specific applications:

PrefixBase 1000Base 10DecimalEnglish wordAdoption[nb 1]
NameSymbolShort scaleLong scale
yottaY 10008 10241000000000000000000000000 septillion quadrillion1991
zettaZ 10007 10211000000000000000000000 sextillion trilliard1991
exaE 10006 10181000000000000000000 quintillion trillion1975
petaP 10005 10151000000000000000 quadrillion billiard1975
teraT 10004 10121000000000000 trillion billion1960
gigaG 10003 1091000000000 billion milliard1960
megaM 10002 1061000000 million1873
kilok 10001 1031000 thousand1795
hectoh 10002/3 102100 hundred1795
decada 10001/3 10110 ten1795
 10000 1001 one
decid 1000−1/3 10−10.1 tenth1795
centic 1000−2/3  10−20.01 hundredth1795
millim 1000−1 10−30.001 thousandth1795
microµ 1000−2 10−60.000001 millionth1873
nanon 1000−3 10−90.000000001 billionth milliardth1960
picop 1000−4 10−120.000000000001 trillionth billionth1960
femtof 1000−5 10−150.000000000000001 quadrillionth billiardth1964
attoa 1000−6 10−180.000000000000000001 quintillionth trillionth1964
zeptoz 1000−7 10−210.000000000000000000001 sextillionth trilliardth1991
yoctoy 1000−8 10−24 0.000000000000000000000001 septillionth quadrillionth1991
  1. ^ Prefixes adopted before 1960 already existed before SI. 1873 was the introduction of the CGS system.
Other Languages
العربية: هكتو
беларуская: Гекта-
български: Хекто-
brezhoneg: Hekto
català: Hecto-
čeština: Hekto
dansk: Hekto
Deutsch: Hekto
eesti: Hekto-
español: Hecto
Esperanto: Hekto
euskara: Hekto
فارسی: هکتو
français: Hecto
galego: Hecto-
한국어: 헥토
հայերեն: Հեկտո
हिन्दी: शत-
Bahasa Indonesia: Hekto-
italiano: Hecto
ქართული: ჰექტო...
қазақша: Гекто-
Кыргызча: Гекто...
lietuvių: Hekto-
മലയാളം: ഹെക്റ്റോ-
Nederlands: Hecto
日本語: ヘクト
norsk: Hekto
norsk nynorsk: Hekto
ភាសាខ្មែរ: ហិកតូ
Plattdüütsch: Hekto
polski: Hekto
português: Hecto
Ripoarisch: Hecto
русский: Гекто-
sicilianu: Hecto
slovenščina: Hekto
کوردی: ھێکتۆ-
српски / srpski: Хекто
svenska: Hekto
ไทย: เฮกโต
українська: Гекто-
Tiếng Việt: Héctô
中文: 百 (词头)