How to make a more complicated version of the if function

Hi,

I would like to make a formula that allows me to have a number set automatically according to the number i put in the previous cell.

Hope you understand what i mean

I want to put a number in cell A1 so that there appears another number automatically in cell A2, this number will depend on the number i put in A1.

Let's say i do this:
I put the number 0 in CELL A1 -----> CELL A2 automatically becomes 0.4
CELL A1 = 0 to / or equal to 1.25 -----> CELL A2 = 1
CELL A1 = 1.25 to / or equal to 3.10 -----> CELL A2 = 2
etcetera....

Sorry for my bad English i'm from Belgium.

Hope you can help me out.