A right tributary of the Inn, the Sims is approximately eight kilometers long, and is fed by the Simssee, a small lake.

[1] It flows into the Rohrdorfer Achen, close to its confluence with the Inn, near Rosenheim in the municipality of St. Stephen's churches.

At its southern end, the Sims flows out of the Simssee to the north of Riedering at 470 m above sea level and immediately heads west through the wet Achalterwiesen meadows in the nature reserve on the southern shore of the Simssee .

Here it picks up a second short outflow of the lake from the right, runs a good distance through the nature reserve and then touches the district of Eitzing on its southern edge at the Krottenhausmühle.

Further downstream, it runs through the Kohlhauf and Pulvermühle sites before entering the forest area around the Lauterbacher Filze, where it picks up the Röthbach flowing in from Riedering-Niedermoosen in the south and then loops around another Stephanskirchen Pulvermühle.