Half Birthday Calculator

A half birthday is 6 calendar months after your birthday, not a fixed 182 days. 6 calendar months span 181 to 184 days, depending on which months they cover. Half of a 365-day year is 182.5 days, so the "exact half" lands 182 or 183 days after your birthday and can differ from the calendar date by 1 or 2 days.

Leap years affect half birthdays only for birthdays on August 29, 30 or 31. Those half birthdays fall in February: on February 28 in a common year and February 29 in a leap year. Every other half birthday keeps the same month and day every year. A February 29 birthday always has its half birthday on August 29.

To find your next half birthday, add 6 months to your last birthday; if that date has passed, add 6 months to your next birthday instead. The calculator does this from today's date and shows the days left. On October 30, 2026, someone born on March 15 has a next half birthday on 15 September 2027, 320 days away.

People celebrate half birthdays for 4 main reasons: summer birthdays that miss the school year, birthdays that clash with holidays, baby milestones and a mid-year excuse to get together. A child born in July celebrates with classmates in January, and someone born on December 25 gets a June 25 celebration of their own.

Your half birthday is 6 months after your birthday, on the same day of the month. Born on April 10? Your half birthday is October 10. Born on October 15? It is April 15. Born on July 22? It is January 22. Enter your date of birth for the exact date and a countdown.

To calculate your half birthday, add 6 to your birth month and keep the same day. Subtract 12 when the month number goes past 12: a November (11) birthday becomes 17 − 12 = 5, May. When that day does not exist in the new month, use the month's last day.

The formula for a half birthday is half month = birth month + 6, minus 12 if the result is over 12, and half day = the smaller of your birth day and the days in the half month. In a spreadsheet, =EDATE(A1,6) returns the half birthday for a date of birth in A1 and handles month ends the same way.

Yes, a half birthday is exactly 6 calendar months after your birthday. It is not always exactly half the days of your birthday year. A March 15 birthday has a calendar half birthday on September 15 and an exact half (182 days) on September 13.

A half birthday is 181 to 184 days after your birthday by the calendar, and 182 or 183 days by the exact-half method. A 365-day year halves to 182.5 days and a 366-day year to 183. The calculator shows both dates, so you can pick the one you prefer.

If you were born on August 31, your half birthday is February 28, or February 29 in a leap year. February 31 does not exist, so the half birthday moves to the last valid day of February. In 2027 it is February 28; in 2028, a leap year, it is February 29.

If you were born on February 29, your half birthday is August 29, every year. August always has a 29th, so leap-day babies get a fixed half birthday even in the 3 years out of 4 when their real birthday is missing from the calendar.

The days until your half birthday are the days from today to the next date 6 months after a birthday, from 0 to 184. Enter your date of birth and the calculator counts them. From October 30, 2026, a March 15 birthday has its half birthday 320 days away.

A baby's first half birthday is the day the baby turns 6 months old: 6 calendar months after the birth date. A baby born on 31 January 2026 has a first half birthday on 31 July 2026. That date often lines up with the 6-month well-baby check, and many parents mark it with a "half cake" photo.