Legal documents, contracts and checks traditionally spell amounts in words to prevent alteration — "1,500.00" is easy to doctor, "one thousand five hundred and 00/100" is not. Many jurisdictions treat the written words as authoritative when the figures and words disagree.

Style guides generally recommend spelling out numbers below ten (or below one hundred, depending on the guide) in prose, and using figures elsewhere. This converter handles values up to 999 trillion including two decimal places.