Question 1

How large a number can I convert?

Accepted Answer

Integers up to 18 digits (up to 999 quadrillion). Negative numbers and zero are supported. Decimals are not — use your local currency formatter for fractional values.

Question 2

Does it use the short scale (billion = 10^9)?

Accepted Answer

Yes — the American/modern English short scale where one billion equals one thousand million, and one trillion equals one thousand billion.

Number to Words