Amount to String Converter

Writing monetary amounts in words is a legal requirement on checks, contracts, invoices, and notarial documents in most jurisdictions. A discrepancy between the numeric and written amount on a check can cause rejection by the bank or, worse, enable fraud through digit manipulation. This tool converts any amount up to 999,999,999,999,999.99 into its grammatically correct written form. It handles currency-specific pluralization rules (e.g., 1 dollar vs. 2 dollars, 1 cent vs. 51 cents) and supports five languages. The algorithm decomposes the number into three-digit groups, applies scale words (thousand, million, billion, trillion), and concatenates the result with proper conjunctions.

Limitations: the converter assumes standard Western numbering (short scale where 1 billion = 10⁹). For languages with gendered numerals (Russian, French), the tool applies the correct gender based on the currency noun's grammatical gender. Fractional parts are always rendered as cents out of 100. Pro tip: always double-check the written amount on legal documents against the numeric figure - courts generally honor the written form when there is a conflict.

The conversion algorithm decomposes the input amount A into its integer part I and fractional (cents) part F:

The integer part I is decomposed into three-digit groups G_k from right to left, where k is the scale index:

Each group G_k is further decomposed into hundreds h, tens t, and ones o:

Where h ∈ [0,9], t ∈ [0,9], o ∈ [0,9]. Special handling applies when t = 1 (teen numbers 10 - 19 use unique words). Scale words are appended per group: k = 1 → thousand, k = 2 → million, k = 3 → billion, k = 4 → trillion. The final string concatenates group words in descending scale order, followed by the currency main unit, then F in words with the subunit name.