Charged characters
As described on the Plans & Pricing page this API is charged on a per character basis. To calculate usage each character you submit in the “text” parameter is counted. You are charged for all characters that you include in a request, even untranslated characters. This includes, for example, whitespace characters, numbers and special characters.

Example:

<p>You &#x00026; me</p>

This is charged as 23 characters.