What Is a Pregnancy Due Date Calculator?

A pregnancy due date calculator is a free online tool that estimates your Estimated Due Date (EDD) — the date your baby is expected to be born — along with how many weeks pregnant you are today and which trimester you are in. Enter the first day of your last menstrual period (LMP), conception date, or IVF transfer date for an instant, personalised result based on the same 280-day formula used by obstetricians worldwide.

How Is a Pregnancy Due Date Calculated?

The standard method is Naegele’s Rule — the obstetric formula used globally by midwives, OB-GYNs, and the NHS:

EDD = First Day of Last Menstrual Period (LMP) + 280 Days (40 Weeks)

Alternative calculation methods:

• Conception date method: Conception Date + 266 days (38 weeks)
• IVF transfer method: Day-5 blastocyst transfer date + 261 days
• Ultrasound dating: Most accurate in the first trimester — your sonographer measures crown-rump length (CRL) to confirm or adjust the EDD

Quick example: LMP = 1 October 2025 → EDD = 28 June 2026 (40 weeks)

Only around 4–5% of babies are born on their exact due date. Most births occur within 2 weeks either side of the EDD — between 37 and 42 weeks is considered a full-term pregnancy.

Pregnancy Trimesters & Key Milestones by Week

Why Use Click2Calculate’s Online Pregnancy Calculator?

• ✅ 3 calculation methods — LMP, conception date & IVF transfer date supported
• ✅ Weeks pregnant today — shows exact gestational age to the day
• ✅ Trimester tracker — instantly shows which trimester you are in
• ✅ Adjusted for cycle length — personalised for cycles shorter or longer than 28 days
• ✅ Conception date reverse calculator — work backwards from your due date
• ✅ Week-by-week pregnancy guide — milestones, development stages & scan dates

Use this free pregnancy due date calculator online to know your EDD, track your pregnancy week by week, and prepare for every milestone between now and your baby’s arrival.

Medical Disclaimer: This calculator provides an estimated due date based on standard obstetric formulas and is for informational purposes only. Due dates are estimates — only around 4% of babies arrive on the exact EDD. Your actual due date may be adjusted by your healthcare provider based on early ultrasound measurements, cycle irregularities, or clinical findings. Always consult your OB-GYN, midwife, or healthcare provider for personalised pregnancy care and accurate gestational dating.