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Enrollment Period Calculator
Find your Medicare sign-up windows.
By Naomi Foster, Contributing Writer, Healthcare
Updated July 2, 2026
Updated July 2, 2026
Find your Medicare sign-up windows.
Educational estimate. Not insurance advice, confirm with plan documents.
Medicare enrollment windows are strict. Missing them can mean lifelong late penalties or a year-long wait. Your Initial Enrollment Period is a 7-month window around your 65th birthday: the three months before, your birthday month, and the three months after. After that, the Annual Election Period (October 15 through December 7) is when most people switch plans for the following year.
If you are already on a Medicare Advantage plan, you also get the Medicare Advantage Open Enrollment Period (January 1 through March 31) to make one change. Certain circumstances, including moving or losing coverage, can open additional Special Enrollment Periods. Confirm your exact dates at Medicare.gov.
None of these windows extend themselves for a holiday, a mailed letter that arrived late, or a form that got misplaced. If a deadline is close, calling 1-800-MEDICARE or your local State Health Insurance Assistance Program office directly is safer than waiting on paperwork to catch up.
For the Initial Enrollment Period, we build the 7-month window around your 65th birthday month. The Annual Election Period and Advantage Open Enrollment are fixed federal dates.
Pick birthday month 6, June, and the calculator counts three months back to March and three months forward to September, giving a window that opens in March and closes in September, with June itself in the middle.
The math also has to wrap around the calendar. Pick birthday month 12, December, and three months back lands in September of the same year, while three months forward lands in March of the following year. The calculator handles that wraparound automatically, so a window can straddle two calendar years without the dates coming out wrong.
Once your dates are set, the cost tools can price out the plans you are weighing.
Once you know your window, work out what a plan will actually cost you with the premium-plus-out-of-pocket cost tool, or weigh Advantage against Medigap with the side-by-side comparison tool. The 2026 cost and enrollment reference lists every federal date and dollar figure this site cites, with sources.
Your IEP runs for seven months total: the three months before the month you turn 65, your birthday month itself, and the three months after. Enroll in the early part of that window and Part B coverage usually starts the month you're eligible; wait until after your birthday month and coverage can be delayed.
AEP is the yearly window, October 15 through December 7, when anyone with Medicare can join, switch, or drop a Medicare Advantage or Part D plan for the following calendar year. Changes made during AEP take effect January 1.
It's a shorter, once-a-year window, January 1 to March 31, reserved for people already enrolled in a Medicare Advantage plan. It lets you make one change: switch to a different Advantage plan or drop back to Original Medicare, with or without a standalone Part D plan.
No. This tool calculates general windows from federal rules; your own dates can shift for reasons like Special Enrollment Periods tied to a move, a loss of coverage, or other qualifying events. Confirm your specific situation at Medicare.gov or by calling 1-800-MEDICARE.