👶 Due Date Calculator
Count down to the big day. Estimate your baby's due date from your last period, a conception date, or an IVF transfer — with the current gestational week, trimester, and days to go.
👶 Your estimate
Based on a 280-day pregnancy from an equivalent last-period date of 2026-10-05. This is an estimate from a date, not a prediction: your doctor or midwife confirms the due date, often with an early ultrasound. Not medical advice.
From two lines to a due date
The classic 40-week count starts from the first day of the last period — about two weeks before conception actually happens. That is why every pregnancy app talks in gestational weeks that run a fortnight “ahead” of the baby's true age, and why an IVF transfer needs the embryo's age folded in to land on the same timeline.
Use the estimate to plan appointments, parental leave, and the nursery — then let your doctor or midwife confirm the dates with an ultrasound, which remains the gold standard for pregnancy dating.
❓ Frequently Asked Questions
How is the due date calculated?
By Naegele's rule: the estimated due date is 280 days (40 weeks) after the first day of your last menstrual period. From a known conception or ovulation date it is 266 days later, and for IVF it is counted from the embryo transfer date, adjusted for the embryo's age at transfer (a day-5 blastocyst is 261 days, a day-3 embryo 263 days).
How accurate is a due date?
It is an estimate, not a promise. ACOG says only about 1 in 20 women give birth on their due dates, and that a first-trimester ultrasound is the most accurate method to establish or confirm gestational age. Irregular periods and uncertain dates shift the estimate, so your doctor or midwife confirms it.
What is gestational age and how does it differ from the baby's age?
Gestational age is measured from the first day of your last period, so at conception you are already counted as about two weeks pregnant. That is why an IVF day-5 embryo shows as roughly two weeks and five days — the calendar counts from the LMP-equivalent date, not the moment of fertilisation.
Which trimester am I in?
By the common convention this tool uses, the first trimester is weeks 1–12, the second is weeks 13–27, and the third is week 28 until birth.
Is this medical advice?
No. It is an informational estimate from a date. Your due date and pregnancy care come from your doctor or midwife. CDC lists urgent maternal warning signs, during pregnancy and in the year after, that need medical care immediately; they are linked on this page.