How many diary of a whimpy kids books are there?

As of my knowledge cutoff in September 2021, there are 16 books in the Diary of a Wimpy Kid series written by Jeff Kinney, including:

1. Diary of a Wimpy Kid (2007)

2. Rodrick Rules (2008)

3. The Last Straw (2009)

4. Dog Days (2009)

5. The Ugly Truth (2010)

6. Cabin Fever (2011)

7. The Third Wheel (2012)

8. Hard Luck (2013)

9. The Long Haul (2014)

10. Old School (2015)

11. Double Down (2016)

12. The Getaway (2017)

13. The Meltdown (2018)

14. Wrecking Ball (2019)

15. The Deep End (2020)

16. Big Shot (2021)

Please note that there might be more books in the series released after my knowledge cutoff. You can check the official Diary of a Wimpy Kid website or relevant book retailers for the latest information.