Number to Words

English has two incompatible ways of naming large numbers, and which one you want depends on where the document will be read. The international system groups digits in threes (thousand, million, billion, trillion) and 10,000,000 is ten million. The Indian system groups differently after the thousands, using lakh (100,000) and crore (10,000,000), and writes the same figure as 1,00,00,000, one crore. Indian banking, legal and government documents use the second throughout, so converting an amount for an Indian cheque with the international system produces a technically readable but conventionally wrong result.

The reason amounts are written in words at all is that words are far harder to alter than digits. A figure can have a zero appended or a decimal point shifted with a pen stroke; "forty-two thousand five hundred only" cannot. This is why cheques, contracts and promissory notes carry both, and why the words legally prevail over the figures in most jurisdictions when the two disagree. The word "only" at the end is part of the same defence: it marks the end of the amount so nothing can be added after it.

The details that make written amounts look right are conventions rather than rules, but they are consistent ones. Compound numbers from twenty-one to ninety-nine are hyphenated. "And" appears before the tens and units in British usage and is generally omitted in American. Currency subunits are usually written separately ("and fifty paise", "and twenty-five cents") rather than as a decimal fraction of the main unit. This converter follows the common banking conventions for each system, which is the form a teller expects to see.