I have to read value from Pressure Transducer which provides output in 4-20mA. Kindly write down the ways to calculate current .
Pressure transducer is two wire 12V operated
Hi,
Can you post a link to the specs/manual for the transducer please?
You should be able to use a 12V supply and a series 250R resistor to develop 1 to 5V from the 4 to 20mA, suitable for the 5V analog input of the Arduino.
What model Arduino are you using?
Thanks.. Tom... 
I would put more protection on that input. Depending on the wiring there is up to 100% probability that the wrong wire will get plugged into 12V.
Maxim makes some nice chips that protect 4-20mA inputs from a wide range of common faults.
Pressure value with a 250ohm resistor and default Aref is supply dependent (USB / external).
I would use a 51ohm resistor for R1 (standard 1% E24 value).
And measure with 1.1volt Aref enabled.
Add a 100n cap between A-in and ground.
Then R2 could be increased to a safer 10k.
With R1 = 51ohm and R2 = 10k, the schottky diode is not needed anymore.
with R1 = 51ohm, input currents of up to ~100mA will stay under the 5.5volt limit of the pin.
Leo..