Maximum value of numerical register

What is the maximum value of a numerical register in R30i B?
Is a register (R[I]) a 32bit memory value?
My specific case is : I am receiving the height of a product as mm x 1000 (1mm = 1000)
This is received by group input of 16bits.
In the controller I will multiply the height by the number of products.
I could for the multiplication continue to work in micrometer as het height was received and at the end divide by 1000 to get
the total height in mm. This should be possible if a register is up to 32bit but not if it is only up 16bit.
So, please advise of the maximum register value
Thanks