🤰 Due Date Calculator
Pick your last period or conception date to see your estimated due date, how many weeks and days along you are today, and which trimester you're in.
Informational estimate only — not medical advice. Always confirm your due date and care with your doctor or midwife.
📅 Estimate Your Due Date
🤰 Your estimate
This is an estimate from a date, not a prediction. Your doctor or midwife confirms the due date, often with an early ultrasound.
What is a Due Date Calculator?
It turns one date you know into the timeline of your pregnancy. Give it the first day of your last period (or the conception date, if you know it) and it applies Naegele's rule — the documented +280-day / +266-day convention — to estimate the due date, then counts forward to today to report your gestational age in weeks and days and the trimester those weeks fall in.
For traveling parents-to-be that timeline matters twice over: most airlines restrict flying somewhere between weeks 28 and 36, and the second trimester is the classic window for a babymoon. Use the estimate to plan — and let your doctor or midwife, not a calculator, confirm the date that counts.
❓ Frequently Asked Questions
How is a due date calculated?
The estimate uses Naegele's rule, the convention obstetric guidance has used for two centuries: add 280 days (40 weeks) to the first day of your last menstrual period. If you know the conception date instead, the calculator adds 266 days (38 weeks) — the same date by a different path, since ovulation typically falls about two weeks after the period starts.
How accurate is the estimate?
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.
How are the trimesters divided?
The calculator follows the commonly published convention: the first trimester covers weeks 0–13, the second weeks 14–27, and the third from week 28 to birth. Enter today's date and it reports your gestational age in weeks and days and which trimester that lands in.
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.