The number of millionaires in the US jumped by 16 per cent last year after slumping by 27 per cent in 2008, a report shows.

Last year, about 7.8 million US households had a million dollars or more in investable assets - not counting capital invested in their primary residence, the report released on Tuesday by the Spectrem Group shows.

That was up by 1.1 million from the year before, when the number of US millionaires fell to its lowest point since 2003, hitting 6.7 million as the US economy stumbled.

"While still well short of its all-time high of 9.2 million in 2007, this year's growth in the millionaire population is nevertheless welcome news for an economy still working to recover," said George Walper, the group's president.

The number of quintuple-millionaire households - with assets worth more than $US 5 million ($5.49 million) - was also up last year, climbing by 17 per cent to 980,000 from 840,000 in 2008.