Max current out of 5v pin on UNO?

How much current can I safely draw from the 5v pin on the UNO when powered from USB or power jack ?

About 450mA from USB and 650mA from power jack. But this last one depends on the input voltage as it is limited by power dissipation. See:-

http://www.thebox.myzen.co.uk/Tutorial/Power_Examples.html

450 should do the trick for a test with a powerled i'd like to do. thx for the fast response.