The young, less educated and those with lower incomes were more likely to give higher estimates, Gallup said Friday.
The poll said 52 percent of those questioned estimate at least one in five Americans is gay or lesbian; 35 percent estimate one in four are gay, while 30 percent put the figure at less than 15 percent.
The findings from the Gallup poll conducted earlier this month mark the second time Gallup has asked Americans to estimate the gay population.
In 2002, Americans estimated 21 percent of men were gay and that 22 percent of women were lesbians.
Demographer Gary Gates last month questioned the accuracy of such high estimates. He said his review of population-based surveys on the topic indicate about 3.5 percent of adults in the U.S. identified themselves as lesbian, gay or bisexual.
The telephone poll was conducted May 5-8 from a random sample of 1,018 adults, age 18 or older. It has a margin of error of plus or minus 4 percentage points.