Enter the first day of the last menstrual period, or a known due date, to see weeks and days pregnant, the trimester, the estimated due date and days remaining.
Dating is based on the standard 280-day (40-week) pregnancy counted from the first day of the last menstrual period, so the due date estimate is the period date plus 280 days. When a due date is entered instead, the weeks pregnant are counted backwards from that date. Trimesters are shown as first trimester up to 13 weeks 6 days, second trimester from 14 weeks 0 days to 27 weeks 6 days, and third trimester from 28 weeks onwards. These are estimates for general information: cycle length, ovulation timing and early scans can shift real dating, and a clinician confirms dating.
Is this calculator medical advice? No. It provides general information and estimates based on standard 280-day dating only. It is not medical advice, and a clinician should confirm dating and any health questions.
Why can the due date estimate differ from a scan date? The estimate assumes a 28-day cycle with ovulation on day 14. Real cycles vary, and an early ultrasound measurement can give a different, often more accurate, due date.