Hi Nisha,
The calculation for productivity can be a simple as the value delivered to your client divided by the cost. The cost is comparatively easy to determine, such as person-hours of effort or money spent. Determining the value delivered is more difficult. A simple example would be to use lines of code (LOC) for the value delivered divided by the number of hours to develop the code. If 1000 lines of code were produced using 10 hours of effort, the productivity is 100 lines of code per hour.
Unfortunately, simple productivity calculations are often misleading at best and counterproductive at worst. In our simple LOC example, the most productive development teams strive to minimize the amount of code, not maximize it. Measuring LOC per hour is therefore misleading and could have the negative consequence of encouraging quantity instead of productivity.
And most clients are not interested in code. They are interested in functionality, quality, etc. I suggest working closely with your client to define your productivity goals, determine a means for measuring your productivity (value delivered and its costs), and periodically reviewing your results and refining your measurements.
Tom