🤰 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
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 a statistical anchor, not a promise — only around one in twenty babies arrives on the estimated date, and most are born within a two-week window either side. Cycle length, irregular periods, and uncertain dates all shift the picture, which is why clinicians usually confirm dating with a first-trimester ultrasound.
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 based on documented rules of thumb. Your actual due date and pregnancy care should always come from your doctor or midwife, who will confirm dating with an ultrasound and your history.