Using the IRR function:
The arguments for the IRR function are:
Argument  Required?  Description 

values  Required  Values must contain at least one positive value and one negative value to calculate the internal rate of return. 
guess  Optional  A number that you guess is close to the result of IRR .
• Excel uses an iterative technique for calculating IRR . Starting with guess , IRR cycles through the calculation until the result is accurate within 0.00001 percent. If IRR can't find a result that works after 20 tries, the #NUM! error value is returned.
• In most cases you do not need to provide guess for the IRR calculation. If guess is omitted, it is assumed to be 0.1 (10 percent).
• If IRR gives the #NUM! error value, or if the result is not close to what you expected, try again with a different value for guess.
