Steinach has a population (as of ) of . , about 21.0% of the population was made up of foreign nationals. Of the foreign population, (), 69 are from Germany, 113 are from Italy, 210 are from ex-Yugoslavia, 47 are from Austria, 63 are from Turkey, and 74 are from another country. Over the last 10 years the population has grown at a rate of 17.6%. Most of the population () speaks German (89.9%), with Serbo-Croatian being second most common ( 3.0%) and Italian being third ( 2.2%). Of the Swiss national languages (), 2,606 speak German, 11 people speak French, 63 people speak Italian, and 6 people speak Romansh.