Pregnancy Due Date Calculator

How your due date is calculated

Naegele’s rule: the first day of your last period + 280 days (40 weeks), ad­just­ed if your cycle is longer or short­er than 28 days. From a known con­cep­tion date, add 266 days. For IVF: day-5 embryo trans­fer + 261 days, day-3 trans­fer + 263 days (ACOG, “Meth­ods for Es­ti­mat­ing the Due Date”).

Preg­nan­cy is dated from the first day of your last period, so at con­cep­tion you’re al­ready about two weeks along.

How accurate it is

Your due date is an es­ti­mate: only a small share of babies arrive on that exact day, and most come within a few weeks of it. A first-trimester ul­tra­sound gives the most ac­cu­rate dating — if your provider gives you a dif­fer­ent date, go with theirs.

Trimesters

First trimester: through 13 weeks 6 days. Second: weeks 14–27. Third: from week 28 until birth. Preg­nan­cy is con­sid­ered term from 37 weeks.

Your privacy

Ev­ery­thing is cal­cu­lat­ed in your brows­er and noth­ing is sent any­where. This cal­cu­la­tor doesn’t assess health or de­vel­op­ment — ask your provider about any­thing to do with how you feel.