Moodle has a default Letter Grade Scale that you can edit to match your Course Grade Scale.

1. Go to the Moodle course you would like to change the letter scale in. Click on Grades in the top navigation menu

 

2. In the Grader report drop down menu, choose Grade letters

 

3. Click the Edit button

 

4. Check the Override site defaults box 

 

5. You will now be able to edit the scale as you would like. Once you are finished, click the Save changes button at the bottom of the page