The son of Michael and Miriam Simon Gratz, Hyman Gratz was raised in a large family, prominent in civic and Jewish communal life in Philadelphia. His father was a merchant and land speculator. Among his siblings were Frances, Rebecca, Benjamin, Rachel, and Joseph.

Educated in Philadelphia public schools, Gratz went into business, from 1798 as wholesale grocer, in partnership with his brother Simon, and later in life insurance. In 1818 he was elected director of the Pennsylvania Company for Insurance on Lives and Granting Annuities, and two decades later became president of the firm.

Like many of his siblings he devoted time and attention to philanthropy: he served on the board of the Pennsylvania Academy of Fine Arts, was one of the managers of the Jewish of the first Jewish Publication Society of America, in the 1840s, and served as treasurer of Congregation Mikveh Israel from 1824 to 1856. In coordination with the Hebrew Education Society of Philadelphia—founded by his sister Rebecca and Rabbi Isaac Leeser—established a trust of stocks, bonds, and other property, to create a “a college for the education of Jews residing in the city and county of Philadelphia.” Opened in 1895, Gratz College has since grown to become a liberal arts college in suburban Philadelphia.