Half Birthday Calculator: When Is My Half Birthday?

Find your half birthday — the date exactly 6 months from your birthday. Enter your birth date to see your half birthday date and countdown. Example: if your birthday is March 15, your half birthday is September 15. Popular for kids' celebrations, classroom milestones, and anyone who loves an extra reason to celebrate!

Half birthday by month: quick reference

Your half birthday is 6 months from your actual birthday. Here's the month conversion — use the calculator for your exact half birthday date:

Your Birthday Month	Your Half Birthday Month	Example
January	July	Jan 15 → July 15
February	August	Feb 10 → Aug 10
March	September	Mar 15 → Sep 15
April	October	Apr 20 → Oct 20
May	November	May 5 → Nov 5
June	December	Jun 1 → Dec 1
July	January (next year)	Jul 4 → Jan 4
August	February (next year)	Aug 15 → Feb 15
September	March (next year)	Sep 1 → Mar 1
October	April (next year)	Oct 31 → Apr 30*
November	May (next year)	Nov 20 → May 20
December	June (next year)	Dec 25 → Jun 25

*Special case: If your birthday is on the 29th, 30th, or 31st of a month, your half birthday may adjust to the last day of the target month. For example, August 31 → February 28 (or Feb 29 in leap years).

Date of birth

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Not sure what year you were born? Browse ages by birth year first.

What is a half birthday and why celebrate it?

Half birthday meaning

A half birthday is the date exactly 6 months from your actual birthday. If your birthday is March 15, your half birthday is September 15. If your birthday is August 31, your half birthday is typically February 28 (or Feb 29 in leap years, since there's no August 31 equivalent 6 months earlier).

Why people celebrate half birthdays

Kids with summer birthdays: Children born in June, July, or August often miss classroom birthday celebrations. Half birthdays let them celebrate at school.
Milestone ages: Kids turning 2.5, 3.5, or 4.5 years old hit developmental milestones worth celebrating
Extra celebration: Some people just love any excuse for cake and gifts!
Adults: Fun way to celebrate a "half year older" or plan mid-year gatherings
Planning: Parents use half birthdays to space out kids' birthday parties

How to calculate a half birthday

Add 6 months to your birthday. The calculator handles varying month lengths automatically. Formula: Birthday + 6 months = Half birthday. If adding 6 months goes into the next calendar year, that's normal (e.g., October 15 + 6 months = April 15 next year).

Fun fact: Half birthdays became popular in schools in the 1990s-2000s as a way to include summer birthday kids in classroom celebrations. Now it's a common tradition for all ages!

More age tools

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Age difference calculator — age gap between two people.
Birthday countdown — days until your next birthday.
Age between two dates — exact difference between dates.
Retirement age calculator — estimate retirement date and time left.
Age in months — your total age in months (and optional weeks and days).

Half birthday calculator: FAQs

What is a half birthday?

A half birthday is the date exactly 6 months from your actual birthday. Example: if your birthday is March 15, your half birthday is September 15. It's popular for celebrating kids with summer birthdays who miss classroom celebrations.

When is my half birthday?

Add 6 months to your birthday month. Use the reference table above for quick month conversions, or enter your exact birth date in the calculator for your precise half birthday date.

Why do people celebrate half birthdays?

Half birthdays are popular for: (1) kids with summer birthdays who miss school celebrations, (2) celebrating developmental milestones (2.5, 3.5, 4.5 years old), (3) adults who love any reason to celebrate, and (4) spacing out multiple kids' birthday parties in the same family.

What if my birthday is on the 31st?

If your birthday is on the 29th, 30th, or 31st of a month, your half birthday adjusts to the last day of the target month. Example: August 31 birthday = February 28 half birthday (or Feb 29 in leap years). January 31 birthday = July 31 half birthday (both months have 31 days).

Is a half birthday exactly 6 months or 182.5 days?

This calculator uses the 6-month method (add 6 calendar months), which is the most common way to calculate half birthdays. Some people use 182-183 days (half a year), but the 6-month method is standard for school celebrations and parties.

Does this calculator handle leap years?

Yes. The calculator accounts for varying month lengths and leap years using standard calendar rules to find your exact half birthday date.

Do you store my birthday?

No. All calculations run locally in your browser. No birth dates or personal data are saved, transmitted, or stored. Full privacy guaranteed. Learn more on our privacy page.