Last year Google launched the ability to make phone calls from Gmail, although it was largely restricted to the US market. From today the service has been opened up further, with support for 38 languages and 4 payment currencies.

Payment can be made in Euros, British pounds, Canadian dollars or U.S. dollars and it opens up the possibility of using Gmail for cheap international calling to far more people than before. As Google notes, “It’s now only $0.10 (or €0.08) per minute to call mobile phones in the U.K., France or Germany (landlines are $0.02/min), $0.15/minute to call mobile phones in Mexico and $0.02/min to call any phone number in China and India.” Full calling rates can be found here.

Calls within and between the US and Canada will continue to be free for the whole of 2011, although you’ll have to pay to call those countries from abroad.

If you’re using Gmail in one of the 38 languages supported, Google says that the feature will be added to your account over the next four days. You’ll need to have the Voice and Video Call Plugin installed for it to work.