数字から通貨表記への変換

Why writing numbers as words still matters

On a paper cheque, in a promissory note, or on a formal invoice, the amount is written twice — once in digits and once in words. The words are the legal authority: if the two disagree, courts and banks treat the spelled-out version as binding, because it is far harder to alter a written phrase than to slip an extra zero onto a figure. This tool converts a number such as 1234.56 into its written form, One Thousand Two Hundred Thirty-Four Dollars and Fifty-Six Cents, handling the grammar, the currency unit, and the cents for you.

How the conversion works

The converter splits your number into the whole part and the fractional part, then names each independently. To avoid a classic rounding bug it first multiplies by 100 and rounds to whole cents, then separates the parts — so a value like 1.999 correctly carries to "Two Dollars" rather than producing "One Dollar and One Hundred Cents". The integer is processed in groups of three digits from the right, each group named with the One…Nineteen and Twenty…Ninety word tables, then tagged with a scale word — Thousand, Million, or Billion — as appropriate. Numbers from 21 to 99 are hyphenated in the conventional way (Thirty-Four), and the supported range runs up to just under one trillion.

The four currencies and how they differ

Two grammatical details are handled automatically: the unit is singular when the amount is exactly one (One Pound, not One Pounds), and the British pound uses "Penny" for one and "Pence" for many. Because the yen has no everyday sub-unit, the tool ignores any decimals you enter for JPY.

A worked example

Enter 1234.56 with USD selected and the currency format produces One Thousand Two Hundred Thirty-Four Dollars and Fifty-Six Cents. The whole part 1234 breaks into the chunk "One" (thousands) plus "Two Hundred Thirty-Four"; the 56 cents become "Fifty-Six Cents". Switch to GBP and the same figure reads …Pounds and Fifty-Six Pence. Tick the Legal / ALL CAPS box and the entire phrase is uppercased — the style many cheques and contracts prefer because capital letters resist tampering. When the cents are zero, the tool writes "and No Cents" rather than leaving the phrase dangling, which is exactly the convention used on cheques.

The ordinal mode

Switch the format to Ordinal Number and the tool drops the currency entirely, instead naming the position: 1 becomes First, 23 becomes Twenty-Third, 100 becomes One Hundredth. It does this by converting to words and then transforming only the final word with the correct ordinal suffix. This is handy for contract clauses ("the Twenty-First day of the month"), rankings, and document section headings.

Use cases and tips

• Cheque writing. Copy the words straight onto the "pay to the order of" amount line; the ALL CAPS option matches common bank formatting.
• Legal and financial documents. Invoices, promissory notes, and settlement agreements all benefit from a spelled-out, unambiguous amount.
• Accessibility and proofreading. Reading a figure aloud in words catches transposed digits a quick glance would miss.

Common mistakes to avoid

• Choosing the wrong currency. The unit word is locked to your selection, so converting a pound amount while USD is selected will say "Dollars". Pick the currency first.
• Expecting yen cents. Decimals are intentionally dropped for JPY; if you need a sub-unit, choose a different currency.
• Exceeding the range. The tool caps at 999 billion and will tell you when a number is too large rather than producing nonsense.
• Relying on it for translation. Output is English only; it spells the words, it does not translate them into other languages.

The conversion runs entirely in your browser, so nothing you type is uploaded — your cheque amounts stay on your device.