The official currency in Bali is the Indonesian Rupiah.
You will get a better exchange rate if you use an official local money changer rather than exchange money in your home country.
There are many money changers offices around the island, but we suggest that you use official offices and stay away from the street money changers who are known to be skilled scammers.
You can also withdraw Indonesian Rupiahs in ATMs. Be careful as well when using an ATM and prefer the ones that are in a bank to avoid extra charges and potential skimming scams.
Here are the IDR exchange rate for some major currencies
1 EUR = 15.500 IDR
1 USD = 14.000 IDR
1 AUSD = 10.000 IDR