👶 Due Date Calculator
Enter the first day of your last period and your average cycle length to estimate when your baby is due, plus the end of your first and second trimesters.
🤰 Estimate Your Due Date
Please note: this calculator is informational only and is not medical advice. Always consult your pediatrician, doctor, or midwife about your pregnancy and due date.
What is a Due Date Calculator?
It projects your baby's estimated arrival by counting 40 weeks forward from the first day of your last menstrual period — the same "Naegele's rule" midwives and doctors use — and nudges the date to account for a cycle that runs longer or shorter than the textbook 28 days.
Use it to plan appointments, leave, and the nursery, and to picture how the pregnancy divides into trimesters. Remember it's an estimate: only a small share of babies arrive exactly on the day, and an early ultrasound gives the most accurate dating.
❓ Frequently Asked Questions
How is my due date calculated?
This tool uses Naegele's rule: it counts 280 days (40 weeks) forward from the first day of your last menstrual period, then adjusts for a cycle that differs from the standard 28 days — a longer cycle usually means you ovulated later, so the due date shifts out by the extra days.
How accurate is a due date calculator?
It's a solid estimate, but only about 1 in 20 babies actually arrives on their exact due date. A first-trimester ultrasound dating scan is more accurate than the last-period method, especially if your cycles are irregular. Treat this as a guide and confirm with your doctor or midwife.
What if I don't remember my last period or my cycle is irregular?
The last-period method assumes fairly regular cycles. If you're unsure of the date or your cycles vary a lot, the estimate will be less reliable — an early ultrasound is the best way to date the pregnancy in that case.
When do the trimesters end?
By convention the first trimester runs through the end of week 13 (about 91 days from your last period) and the second through the end of week 27 (about 189 days), with the third trimester carrying through to birth. This tool shows both boundary dates alongside your estimated due date.