From the office of the Kansas AARP: 

AARP Kansas would like to share a new tool developed to help individuals with a Medicare Prescription Drug plan to help Medicare recipients understand their potential drug costs and the time when they may fall into the “doughnut hole”.  The doughnut hole refers to a coverage gap within the defined standard benefit under the Medicare Part D prescription drug program. Under the defined standard benefit package, there is a gap in coverage between the initial coverage limit and the catastrophic coverage threshold. Within this gap, the beneficiary pays 100% of the cost of prescription drugs before catastrophic coverage kicks in.

The tool, called the AARP Doughnut Hole Calculator, is available at www.aarp.org/doughnuthole. Put in your zipcode, your insurance plan, find your medications, and see your cost options.  It's easy-to-use and a great way to compare plans and costs.