making a 220 V step down transformer

hello!

what are the computations involved in making a step down transformer?

and how do we determine the KVA rating of transformer? Is it the same with the voltage input?

hope u people can help me with these questions.. thanks..

At the very least you would need to know -

Nominal and actual supply voltage
Desired secondary voltage.
How much current - usually determined by the load
Characteristics of the load (is it a light, motor ....)

If it is part of the main power distribution system it would be wise to check local codes. Use equipment that is made for the intended purpose. Manufacturers or distributors often provide applications literature to help with sizing.