Choose conception dating or IVF transfer dating
Use the conception method when you have the conception date, and the IVF method when you have an embryo transfer date and embryo age. An intercourse date is not automatically a known conception date. For a frozen embryo transfer, use the dating information supplied by your clinic.
How Pregnancy Due Date & Milestone Calculator works
The Pregnancy Due Date & Milestone Calculator estimates your expected due date (EDD) and current gestational age using three clinically recognised methods: Naegele's Rule (from LMP), conception date calculation, and IVF embryo transfer dating. Each method is internationally recognised for establishing gestational age during prenatal care.
Naegele's Rule — the most widely used method — adds 280 days (40 weeks) to the first day of the last menstrual period, based on the assumption of a 28-day cycle with ovulation at Day 14. When an estimated conception date is supplied, 266 days (38 weeks from conception) are added instead. For IVF pregnancies, the transfer date plus 266 days minus the embryo age at transfer provides an embryo-age-adjusted estimate.
Follow your pregnancy with gestational age in weeks and days, a trimester progress bar, a milestone timeline, and fun baby size comparisons. Use the results to plan ahead and prepare for prenatal appointments.
How to use Pregnancy Due Date & Milestone Calculator
1. Select your dating method
Choose from three tabs: "By Last Period" for Naegele's Rule, "By Conception Date" if you know when conception occurred, or "By IVF Transfer" for IVF pregnancies with known embryo age at transfer.
2. Enter the relevant date
Enter your LMP, estimated conception date, or embryo transfer date. For IVF, select the embryo age your clinic uses for dating; the calculator supports days 2–7.
3. View your due date and gestational age
The calculator immediately displays your estimated due date, a live countdown, your current gestational age in weeks and days, and your current trimester.
4. Explore milestones and baby size
Scroll through the milestone timeline to see when key prenatal events occur, and check the baby size comparison widget that shows your baby's approximate size as a familiar fruit or vegetable.
Key features and technical specifications
Naegele's Rule & Three Dating Methods
Supports LMP-based Naegele's Rule (LMP + 280 days), conception-date calculation (+ 266 days), and IVF transfer dating with embryo age adjustment.
Current Gestational Age Display
Shows precise gestational age in weeks and days, updated in real time based on today's date.
Trimester Progress Bar
Visual three-stage progress bar clearly indicates which trimester (1st, 2nd, or 3rd) the current gestational age falls within.
Baby Size Comparison Widget
Week-by-week fruit and vegetable size comparisons (e.g., "Size of a lemon at Week 14") make gestational progression tangible and engaging.
Pregnancy Milestone Timeline
Approximate gestational timeline with screening discussion, an anatomy scan window, third trimester onset, and term dates. Timing and care vary by individual circumstances and local practice.
Plan your pregnancy with the right dating method
Choose the date you know: the first day of your last period, your estimated conception date, or your IVF transfer date and embryo age. The calculator converts it into a due date and gestational age so you can follow your progress and plan prenatal appointments. Share your selected method and results with your maternity care team when confirming pregnancy dating.
Newly pregnant — establishing a due date
Calculate your EDD immediately after a positive pregnancy test before your first prenatal appointment, using Naegele's Rule.
IVF pregnancies
Estimate your due date using the transfer date and clinic-confirmed embryo age. For frozen transfers, ask your clinic which dating age to use.
Sharing pregnancy news
Confirm gestational age and trimester for sharing pregnancy announcements or discussing your stage of pregnancy with family and care providers.
Pregnancy Due Date & Milestone Calculator reference table
| Input or option | Reference | What to check |
|---|---|---|
| Dating input | Anchor selected in the calculator | Use the matching dating convention |
| Cycle length | Assumption about timing | Actual ovulation can differ |
| Due-date estimate | Projected calendar milestone | Clinical dating can revise it |
Frequently asked questions
How do I use a due date calculator by conception date?
Select By Conception and enter the known conception date. This calculator adds 266 days to estimate the due date, instead of adding 280 days to that date as if it were the start of a last period. If the date you know is intercourse rather than conception, use it only as an approximate reference and follow your clinician’s established dating.
If I conceived today, when is my due date?
Your estimated due date is 266 days from today. Select By Conception Date and enter today’s date to see the calendar date and milestones. This uses an estimated fertilization date, rather than assuming intercourse today necessarily means conception today.
How do I use an IVF or FET due date calculator?
Select By IVF Transfer, enter the transfer date and choose the embryo age used by your clinic for pregnancy dating. The tool adds 266 minus that age in days: 261 days for a day-5 embryo or 263 days for a day-3 embryo. Frozen storage time is not added to embryo age. Keep your clinic’s established due date as the reference for care.
What is Naegele's Rule?
Naegele's Rule is the standard obstetric formula for estimating the due date from the last menstrual period. It adds 280 days (40 weeks) to the LMP date, based on the assumption of a 28-day cycle with ovulation at Day 14. The formula is named after German obstetrician Franz Karl Naegele and has been in clinical use since the 19th century.
How accurate is the calculated due date?
The calculator uses standard pregnancy dating formulas to estimate your due date from the information you enter. The exact day of birth can vary. Your maternity care team can confirm or adjust pregnancy dating using ultrasound and your pregnancy history.
What is gestational age vs. fetal age?
Gestational age counts from the first day of the LMP — approximately 2 weeks before fertilisation — and is the standard clinical dating convention used by obstetricians. Fetal age (or embryonic age) counts from the actual date of fertilisation and is approximately 2 weeks less than gestational age. All weeks referenced by OB-GYNs and ultrasounds use gestational age.
What is the difference between the three dating methods?
Last-period dating adds 280 days to your LMP, assuming a 28-day cycle. Conception dating adds 266 days to your estimated conception date. IVF dating adds 263 days after a day-3 transfer or 261 days after a day-5 transfer.
When do the trimesters start and end?
The first trimester ends at 13 weeks and 6 days. The second runs from week 14 through 27 weeks and 6 days, and the third starts at week 28. These weeks use gestational age, counted from the last menstrual period.
Do I need an internet connection, and are my inputs uploaded?
An internet connection is required to open tools and refresh a temporary session. Processing stays on your device; the handshake sends a random challenge, not files or text inputs. Libraries, fonts or models may download. Local processing cannot remove risks from an untrusted device or extension.
Further reading
Explore the methods and guidance behind this topic in these independent sources.