Formula to work out automatically the grades from marks scored on a paper

Hello,

I am marking my students grades Is they a formula that will automatically put the grade in if a criteria is met for example

0-10 = U
11-15 - G
16 - 20 =F
21-25 = E
......

65+ = A*

Thank you in advance

Steve

Amusing the criteria is in A1 use this

=IF(A1<=10,"U",IF(A1<=15,"G",IF(A1<=20,"F",IF(A1<=25,"E"))))

Add other levels in the similar fashion.