| Forsmarksån | |
|---|---|
|   | |
|   | |
| Location | |
| Country | Sweden | 
| County | Uppsala | 
| Physical characteristics | |
| Mouth | Öregrundsgrepen | 
|  • coordinates | 60°20′28″N18°14′00″E / 60.34111°N 18.23333°E | 
|  • elevation | 0 m (0 ft) | 
| Length | 10 km (6.2 mi) | 
| Basin size | 375.5 km2 (145.0 sq mi) [1] | 
| Discharge | |
| • average | 2.8 m3/s (99 cu ft/s) |