Large Number Converter

[Please note first] This app rewrites the name of a place value between Japanese and English, and nothing more. It does not convert currencies such as dollars and yen. Data sizes such as KB, MB and GB, Japanese numerals written in kanji, and exponent notation such as 1.5x10⁹ are all out of scope. The old Buddhist number names larger than kei are left out because the sources disagree. ────────── ≫ Large Number Converter - a billion is 10 oku Not one oku, and not one cho. Japanese changes the name of a place every four digits and English every three, so the two ladders never line up. Enter one number, pick two places. Ten places, in any direction. ■ Four digits in Japanese, three in English Japanese climbs man, oku, cho, kei, four digits at a time. English climbs thousand, million, billion, trillion, three at a time. The steps are different widths, so the places do not meet. ■ Only one pair matches exactly 1 million is 100 man. 1 billion is 10 oku. 1 trillion is 1 cho. 1 quadrillion is 1,000 cho. Of the ten places, only cho and trillion sit one on one. Both are ten to the twelfth. Leaving one aside, twelve is the only exponent here that both four and three divide. ■ English has no single word for oku One oku is 0.1 billion, which no one says, so English says 100 million. One of the places Japanese uses most often can only be said as a hundred times a million. ■ The commas fall in different places The same number is 100,000,000 in the English style and 1,0000,0000 in the Japanese one. English commas do not sit on the Japanese places, which is what makes them hard to count. This app prints the English three-digit style. ■ Ten places one, thousand (sen), man, million, oku, billion, cho, trillion, quadrillion, kei Enter one and the other nine line up at once. 1 kei is 10 quadrillion, or 10,000,000,000,000,000 written out in ones. Every place is a power of ten and a defined value, so nothing is rounded. ■ Good for ▪ Turning the "1.2 billion" in a foreign news story into oku ▪ Rewriting a figure in cho for an English report ▪ Counting English commas without counting digits by hand ■ Things worth knowing (included in the app) ▪ Japanese changes place every four digits, English every three ▪ Cho and trillion are the only exact match ▪ A billion is 10 oku; one oku is 0.1 billion, so English says 100 million ▪ The commas differ: 100,000,000 and 1,0000,0000 are the same number ■ How the app is built ▪ A single screen and no settings page ▪ Ten common values, each one tap away ▪ Your last five entries are kept and can be tapped to restore ▪ One tap copies the result ▪ Japanese and English, following your device language ▪ No account needed. The conversion runs on your device and the number you type is never sent anywhere ────────── Note: this app rewrites the name of a place value and nothing more. Currency conversion, data size units, kanji numerals and exponent notation are out of scope, and so are numbers that carry a counter or a currency. In present-day English a billion is ten to the ninth, and no older usage is included here.