What percent of the world is gay?

Answers vary greatly. Here are some studies done:

The more rigorous studies have shown different results within a range of 0.6 to 5.4 percent. These studies include Bell-Weinberg, 1970 (~2 percent); Billy-Battelle, 1993 (1.1 percent); Cameron-Ross, 1975-78 (~3 percent); Catania-NABS, 1992 (2 percent); FRI, 1983 (5.4 percent); MacDonald, 1988 (2 percent); NCHS, 1988-91 (3.5 percent); Schmidt, 1987 (0.6 percent); and Trocki, 1988-89 (3 percent).
There are also other studies and reports that have influenced the popularly reported percentage. The popular estimate that 10 percent of the male population and 5 to 6 percent of the female population are exclusively or predominately gay/lesbian is based on the Kinsey Institute data published in 1948. Since then Kinsley has been widely debunked, as more than 55% of the men surveyed were either prisoners, sex offenders, or male prostitutes.

Laumann and Associates (1994), using the national probability Health and Social Life Survey combined with data collected in the General Social Survey, found that 2.8 percent of men and 1.4 percent of women identified as gay or lesbian, while 7.7 percent of men and 7.5 percent of women reported homosexual desire.

Michaels (1996) analyzed the limited available data and estimated that in the United States 9.8 percent of men and 5 percent of women report same-gender sexual behavior since puberty; 7.7 percent of men and 7.5 percent of women report same-gender desire; and 2.8 percent of men and 1.4 percent of women report homosexual or bisexual identity. An analysis of U.S. census data has provided the most solid evidence of the presence and certain social characteristics of lesbians and gays among the general population.

In the 1990 census, gay and lesbian respondents could identify themselves as unmarried partners. Estimates from the 1990 census indicate that 1.63 percent of people aged 15 and older nationwide reported themselves as unmarried partners of the householder. Certain areas have higher percentages.

In 2006 San Francisco reported the highest percentage of individuals identifying as gay, lesbian, or bisexual (15.9 percent). Seattle reported 12.9 percent. Higher percentages may sometimes be offered on the basis that homosexuality will not be acknowledged by all respondents because it carries a social stigma and the threat of persecution.
for women 13% and for men 38%
Most scientists believe that between 4% and 10% is gay, lesbian, and another 25% or so is bisexual.
Scientists estimate human population to be between 4% and 10%. According to US Census bureau, the current world population is estimated at: 6,900,385,814. the minimum 4% then would be: 276,015,433.