The Australian dollar has hit a 10-year low against the US dollar, after New Zealand's central bank unexpectedly cut interest rates by half a per cent.

This is the lowest level for the Australian dollar against the US Dollar since March 2009, during the economic fallout from the global financial crisis.

CommSec's chief economist Craig James said the lower dollar would come as a relief for the Reserve Bank of Australia and other economic policymakers, even if it may be a headache for Australians travelling overseas.