Half Birthday Calculator

About this calculator

Your half-birthday falls exactly six months from your actual birthday — the date arithmetic is simple, but pinning it down precisely gets slightly fiddly for people born on the 29th, 30th, or 31st of a month, since not every month six months away has that same date, which is where a dedicated calculator earns its keep over doing the math by hand.

Enter your birthday and a reference date, and the calculator returns your half-birthday, the next upcoming occurrence of it, and the number of days remaining until then. Parents tracking a young child's growth milestones on a six-month cadence, people planning a half-birthday celebration, and anyone marking the exact midpoint of their personal year use it as a lighthearted way to celebrate — or plan around — the date that splits the year to your next birthday exactly in two.