Below is a yield to maturity calculator. The maturity date must be a positive number–if your issue is a ‘perpetual’ preferred and is past the 1st call date you will have to determine when you are guessing it will be called (a date in the future).
In the ‘years to maturity’ blank you can use decimals–i.e. for 3 months use .25.
Yield to Maturity Calculator
