The Census Bureau released revised estimates Tuesday for the number of same-sex households in the United States, showing a total of 646,000 such households nationwide, down 28 percent from its original calculation.

The new results derived from the 2010 Census are closer to the figures from the bureau’s American Community Survey and reflect an inconsistency in census responses that “artificially inflated the number of same-sex couples,” the bureau said Tuesday in a new report. The Census Bureau had estimated this summer that there were 902,000 same-sex households nationwide.

The revision shows that the number of same-sex households in the United States jumped 80 percent from a decade ago, though it remains a small fraction of all households. The number of unmarried partners rose 64 percent, while the number who said they consider themselves married almost tripled.

The number of married same-sex couples is almost certainly higher since the survey. The census was taken in April, when gay marriage had been legal in the District for less than a month. Since then, New York state has become the seventh and largest jurisdiction in the country to legalize gay marriage.

The bureau’s latest report said same-sex couples account for 0.55 percent of households in the United States. That’s about the same share as in 2000, when it estimated there were about 358,000 same-sex households across the country.

The latest figures include not only new statistics on the number of married couples but also a set of estimates that accounts for errors in capturing data on married and unmarried same -sex partners, the Census Bureau said.

Martin O’Connell, chief of the fertility and family statistics branch of the bureau’s Social, Economic and Housing Statistics Division, unveiled the new report in a conference call with reporters.

Demographers say more same-sex couples are providing information in response to an aggressive outreach effort by the Census Bureau and growing public acceptance.

The bureau says the 2010 Census marks the first time that figures are broken down by whether couples reported themselves as living together as spouses or unmarried partners. Data from the 2000 Census combined the two household types, since there were no states then that performed same-sex marriages.

Now, same-sex couples are legally allowed to marry in six states — Connecticut, Iowa, Massachusetts, New Hampshire, New York and Vermont — plus Washington, D.C.

According to state data released last month by the Census Bureau, the number of same-sex couples increased 51 percent in Maryland and 49 percent in Virginia from a decade ago, accounting for 1.5 percent and 1.2 percent of all couples in the two states, respectively. At the same time, the number of heterosexual couples in both states increased only modestly.

The bureau reported separately last month that U.S. marriages are at an all-time low and that people are waiting longer before marrying for the first time. Only 52 percent of adults 18 and older said they were married, compared with 57 percent in 2000, the Census analysis showed.

Growing cultural acceptance of same-sex couples reached a milestone last week when the U.S. military formally ended its 18-year “don’t ask, don’t tell” policy, which barred gay service members from revealing their sexual orientation. The end of the policy has allowed same-sex military couples to come into the open after years of hiding their relationships.

The new Census report said its “preferred estimates” now show the number of same-sex households with unmarried partners totaling 514,735 nationwide, with 131,729 additional same-sex households made up of spouses. The previous estimates, based on “summary file counts,” showed unmarried partners accounting for 552,620 same-sex households, while spouses made up 349,377.