Seiko Cal. 6R20 is a midrange automatic movement produced by Seiko Instruments Inc. (SII) for Seiko watches. Like other Seiko 6R movements, it is more refined and accurate than the related Seiko 4R series and uses a Spron 510 mainspring. Unlike Cal. 6R15, it is a “Hi-Beat” movement operating at 28,800 A/h and has complications: Subdial day by pointer at 3:00, subdial date by pointer at 6:00, and clockwise power reserve pointer at 9:30.
Cal. 6R20 was introduced around 2007 and remains in production today. It has 29 jewels and 208 parts. It was the basis for the 8R chronograph movement family. Cal. 6R20 was used in the Premier Automatic watches, models SPB001J1, SPB003J1, and SPB005J1, produced October 2007 through July 2011.
According to Seiko documents, this is a modular movement based on Cal. 6R15 but with a Hi-Beat balance and hacking seconds. Cal. 6R21 is similar but reverses the power reserve indicator to counter-clockwise and moves it to 9:00 on the dial.
| Jewels | Components | Speed | Power | 3:00 | 6:00 | 9:00 | |
| 6R15 | 23 | 168 | 21,600 | 50 | Date Window | ||
| 6R20 | 29 | 208 | 28,800 | 45 | Day Subdial | Date Subdial | Clockwise Power Reserve |
| 6R21 | 29 | 208 | 28,800 | 45 | Day Subdial | Date Subdial | Counter-Clockwise Power Reserve |
| 6R24 | 31 | 224 | 28,800 | 45 | Retrograde Day | Retrograde Date | Clockwise Power Reserve |
| 6R27 | 29 | 28,800 | 45 | Date Subdial | Counter-Clockwise Power Reserve | ||
| 6R35 | 24 | 21,600 | 70 | Date Window |