TreeetSpanish tools
números a letras, DNI, RUT and CUIL
Write amounts in Spanish words for cheques and invoices, and work out or check the check digits of Spain’s DNI and NIE, Chile’s RUT and Argentina’s CUIL and CUIT. Everything runs in your browser.
Numbers to Spanish wordsType an amount and get it in Spanish words, ready for a cheque or invoice. 
DNI and NIE letter calculatorType a DNI or NIE number to get its letter, or a full DNI to check it. Chile RUT check digitType a RUT to get its check digit, or a full RUT to check it. CUIL and CUIT check digitCheck a full CUIL or CUIT, or get the check digit from the prefix and DNI. Tools for Spanish-speaking countries: writing amounts in words for cheques and invoices, and the check digits of national ID and tax numbers in Spain, Chile and Argentina. Each runs in your browser.
Which tool for which job
- Números a letras: an amount in Spanish words, with the cents as a fraction (50/100 M.N.) or in words, in pesos, dollars, euros, soles and more.
- DNI and NIE letter: the control letter of a Spanish DNI or NIE, or a check of a full DNI/NIF.
- Validar RUT: the dígito verificador of a Chilean RUT, or a check of a full RUT.
- CUIL and CUIT: an Argentine CUIL or CUIT from a DNI, or a check of a full number.
What the ID tools can and can’t do
Check digits catch typing mistakes: if one digit is wrong, the check digit no longer matches. They don’t prove a number was issued to anyone, and the tools don’t look up names. For official records, use the government office or website that issues the number.
Questions
Do these tools look up whose ID number it is?
No. They only check that a number is well formed. Nothing is looked up or sent anywhere.
Which countries are covered?
Numbers to words works for any Spanish-speaking country, with pesos, dollars, euros, soles and more. The ID tools cover Spain, Chile and Argentina.
Is my ID number stored?
No. Nothing is stored or sent; the calculation runs in your browser.
Do the words follow RAE rules?
Yes. Números a letras follows the Real Academia Española rules, such as veintiún mil and un millón de pesos.