King David is one of the best established examples of gematria. This was the first place I ever learned about adding up the values of letters.

It is right in the first chapter of the New Testament. Matthew gives the generation of Jesus and emphasizes the number 14.

So all the generations from Abraham to David are fourteen generations; and from David until the carrying away into Babylon are fourteen generations; and from the carrying away into Babylon unto Christ are fourteen generations. Matthew 1:17

14 is the number of David. 

Dalet ד 4

Vav ו 6

Dalet ד 4

Total ד+ו+ד 14

Also fun, if we take the name "David son of Jesse" we would get 14+52+320=386.

That is the same as Yeshua which is the Hebrew name of Jesus. 

Yod י 10

Shin ש 300

Vav ו 6

Ayin ע 70

Total י+ש+ו+ע 386