Birthday Rule Calculator: Find Your Medigap Switching Window

This birthday rule calculator tells you whether your state gives Medigap policyholders a yearly, birthday-based chance to change policies without health questions, and if it does, the exact dates of your next window. Pick your state, enter your date of birth, and the tool shows the window, what you can switch to, which insurers count and the official source. Every state rule in it was read on a state insurance department, statute or legislature page. If we could not verify a rule, the tool says so instead of guessing.

How to use the birthday rule calculator

The birthday rule calculator needs two things: the state you live in and your date of birth. Then:

1. Choose your state. The list covers all 50 states and the District of Columbia. Use the state where you live now. Delaware and Nevada say their rule does not follow you if you bought a policy there and moved away.
2. Enter your date of birth. The tool works out your next birthday, then applies your state’s counting rule.
3. Read the result. In a birthday rule state you’ll see the exact first and last day of your next birthday rule window, whether it is open now, what you can switch to, which insurers count, any extra conditions and a link to the official source.

If your state has a different kind of protection, such as Missouri’s anniversary rule, the tool explains it instead. If we found no birthday rule on an official source, it says so and lists the federal guaranteed issue rights. Nothing you type is stored or sent anywhere.

How the birthday rule calculator counts your window

States describe their windows in five different ways, and small wording differences move the last day. The birthday rule calculator follows each state’s own words:

• A set number of days starting on your birthday (California, Idaho, Illinois, Louisiana, Oklahoma, Virginia, Wyoming). Your birthday is day one. A 63-day window that starts on December 31 ends on March 3.
• Your birthday plus a set number of days after it (Maryland, Utah, and Kentucky as we read it). Maryland’s window is “your birthday and the 30-day period following,” so it runs 31 calendar days.
• Days before and after your birthday (Delaware, Oregon): 30 days before through 30 days after.
• From the first day of your birthday month (Nevada, West Virginia).
• Calendar months (Indiana): one month before your birthday through one month after. If the matching day doesn’t exist, as with a March 31 birthday, the tool uses the last day of that month.

Where a state says “at least” a number of days, the tool shows the minimum. For leap-day birthdays in years without February 29, no rule we read says which day counts, so the tool uses February 28 and tells you so. The birthday rule calculator always shows the next window that hasn’t closed, and counts the days left if it is open today.

Hypothetical example: an Oregon birthday rule window

Hypothetical example. Linda lives in Oregon. She was born April 10, 1955, and has Medigap Plan G. She checks the tool on October 15, 2026.

Step 1: her rule. Oregon’s rule, OAR 836-053-0143, gives an annual chance to apply for a new Medigap plan 30 days before and 30 days after the birthday, for a plan of equal or lesser value, with the same or a new company.

Step 2: which birthday. Her 2026 window closed in May 2026, so the next one is for her April 10, 2027 birthday.

Step 3: the dates. Thirty days before April 10 is March 11, because April 1 through 10 is 10 days and March 11 through 31 is 21 days. Thirty days after April 10 is May 10. Her medigap birthday rule dates are March 11, 2027 through May 10, 2027, which is 61 calendar days counting both ends.

Step 4: what she can do. She can stay with Plan G at a lower-priced company, or step down to a plan of lesser value such as Plan N. She can’t move up to a richer plan without health questions.

By comparison, an Idaho resident born December 31, 1956 gets a 63-day birthday rule window from December 31, 2026 through March 3, 2027.

Birthday rule window by state: the data behind the tool

We read every row below on a state insurance department, statute, legislature or State Health Insurance Assistance Program (SHIP) page in October 2026.

Two notes. Indiana’s current window applies to policies delivered, issued or renewed on or after March 15, 2026, replacing an earlier 60-day version. Kentucky’s statute says “within sixty (60) days of” your birthday without saying before or after; the tool counts 60 days after and flags it.

For a plain-language explainer on how these laws work, see our Medicare supplement birthday rule guide.

Anniversary, year-round and other state rules

Some states help people switch medigap plans in other ways:

Massachusetts residents can read more in our Massachusetts Medicare supplement plans guide.

If your state has no birthday rule

For every other state, the tool reports: “No birthday rule found in official sources; check with your state insurance department.” Some states have no rule; in others, one may exist that we couldn’t confirm. Your SHIP, at shiphelp.org, can tell you for free.

You can still switch medigap plans at any time, but outside a protected window the new insurer may ask health questions and can say no. Federal law also gives everyone guaranteed issue rights in specific situations. The CMS guide Choosing a Medigap Policy lists them on pages 17 and 18, including when a Medicare Advantage plan leaves your area, when employer coverage that pays after Medicare is ending, trial rights if you leave Medicare Advantage within your first year, and when a Medigap insurer goes bankrupt. Depending on the situation, you can apply as early as 60 days before the old coverage ends, and no later than 63 days after it ends.

Our Medicare supplement underwriting guide covers the health questions you can expect. If your Medicare Advantage plan is leaving, read what to do when a Medicare Advantage plan is not renewing.

Limits of this birthday rule calculator

• It doesn’t know your policy. West Virginia requires 24 months in force; Oklahoma and Maine require no gap over 90 days; Missouri depends on your policy anniversary. Check those yourself.
• “Same or lesser” varies. Maryland and Idaho publish their own charts of allowed switches. Kentucky, Indiana and Virginia allow only the same benefits.
• It shows the minimum. Where a law says “at least” or “or more,” insurers may give longer.
• Rules change. Indiana amended its window within months of launch. Always open the source link before you act.
• It’s not advice about which plan to buy. It only tells you when you can apply without health questions.

The CMS guide also notes that if you’ve had your current policy less than 6 months, the new one may make you wait for pre-existing condition coverage.

Checklist before you switch medigap plans

• Run the birthday rule calculator and put both dates on your calendar.
• Open the official source link and read your state’s wording.
• Find your current plan letter, premium and policy start date.
• Watch for the insurer’s notice, where your state requires one.
• Get quotes for the same plan letter from several insurers, and a lesser plan if allowed.
• Apply inside your birthday rule window, and keep a copy of the signed application.
• Don’t cancel your old policy until the new one is approved. CMS says you get a 30-day free look period and may pay both premiums for one month.
• Ask your old insurer to end coverage once the new policy is in force.

Birthday rule calculator: frequently asked questions

Does the birthday rule calculator work if I have Medicare Advantage?

No. Birthday rules are for people who already have a Medigap policy. Indiana SHIP says its rule doesn’t give Medicare Advantage members a right to join Medigap. Leaving Medicare Advantage has its own timing; see our guide to how to change Medicare plans.

What if my birthday rule window already closed this year?

The tool skips to next year’s window. Outside it, you can still apply, but the insurer can use medical underwriting.

Can I use the birthday rule window to upgrade from Plan N to Plan G?

Not in the states we reviewed. They allow the same or lesser benefits, and West Virginia’s law says it does not permit buying greater benefits.

What happens to the birthday rule window if I move?

The rule of your new state applies. Delaware and Nevada say their rule doesn’t cover people who bought a policy there and now live elsewhere. See Medicare when moving to another state.

Why are the medigap birthday rule dates different from what my insurer said?

Insurers may give more time than the law’s minimum. Follow the insurer’s written notice, or ask your state insurance department.

Does the birthday rule lower my premium?

Not by itself. Insurers can still price by age, gender, zip code and tobacco use, as Indiana SHIP notes. Savings come from a cheaper insurer or a lesser plan; our Plan G vs. Plan N comparison explains that trade-off.

Want help using your window?

A birthday rule only helps if you apply in time and pick the right policy. Octans Insurance is an independent agency based in Massachusetts. Our licensed agents can check the dates from the birthday rule calculator against your state’s current rules, compare Medigap quotes from the carriers we work with, and walk you through a switch, at no fee. Call (617) 935-9220. For free, unbiased counseling, you can also contact your SHIP at shiphelp.org or call 1-800-MEDICARE (1-800-633-4227).

Keep Reading: Related Guides

• Medicare supplement birthday rule
• Medicare supplement underwriting
• Medicare Plan G vs Plan N
• What are Medicare supplements?

We do not offer every plan available in your area. Please contact Medicare.gov or 1-800-MEDICARE to get information on all of your options.

This article is for general information and is not tax, legal, or medical advice.

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