Enter your timeline
Choose one method and enter the date. We use UTC dates to avoid daylight saving time drift.
Results
Enter your dates above and press calculate to see your estimated due date and milestones.
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Estimated Due Date
Gestational age today
Equivalent dates
- Equivalent LMP:
- Equivalent conception:
Key milestones
- Start of 2nd trimester (14w0d)
- Start of 3rd trimester (28w0d)
- Early term (37w0d)
- Full term (39w0d)
- Late term (41w0d)
- Postterm (42w0d)
Milestone timing varies by clinical guideline and individual pregnancy factors.
For information only; not a medical diagnosis. Speak with your clinician for personalised guidance.
How to interpret the result
A due date is an estimate. Different input methods can give different answers because they anchor pregnancy timing differently.
Which method should I use?
- LMP (Last Menstrual Period) is common when you know the first day of your last period. Cycle length adjusts the assumed ovulation date.
- Conception / ovulation can be more direct if you tracked ovulation (for example, LH tests or basal body temperature).
- IVF / embryo transfer is often the most precise because transfer date and embryo age are known.
- Ultrasound works from the gestational age measured on the scan date and is often used clinically to confirm or revise dating.
Why cycle length matters (LMP mode)
The “40 weeks” rule assumes a 28-day cycle with ovulation around day 14. If your typical cycle is longer or shorter, the estimate shifts by roughly (cycle length − 28) days.
Mini examples
- Conception date known: enter the ovulation/conception day and the tool adds about 266 days (38 weeks).
- Ultrasound: if your scan says 12w3d on the scan date, we count forward to 40w0d.
- IVF day-5 transfer: enter the transfer date and embryo age 5 days; the tool accounts for embryo age when estimating the due date.
References
When to use this calculator
Use this page when you need one pregnancy timeline from a known starting point such as LMP, conception, ultrasound, or embryo transfer. It is the right page when the question is “what date range follows from this record?” rather than “how many days are between two dates?”
Recommended workflow
- Choose the input mode that matches the strongest evidence you already have: IVF or ultrasound before an uncertain LMP.
- Enter one clean date set and check the gestational age and due date together before you share the result.
- Use the notes section to compare methods only after you have one baseline estimate.
When to open a different page
- Open Date Difference when you only need elapsed days between appointments.
- Open Business Days when scheduling leave, paperwork, or weekday-only follow-up.
- Use the Date & Time topic hub when you need the broader workflow for deadlines, time differences, or schedule planning around appointments.
- Stay with medical guidance instead of any calculator when dating decisions affect care plans.
FAQ
How is the due date calculated?
From LMP we add 280 days (40 weeks). From conception or embryo transfer we add 266 days (38 weeks). From ultrasound we work backwards from the gestational age on the scan date.
Can I rely on this as medical advice?
No. Only a qualified healthcare professional can provide personalised medical advice. Use this tool as a planning guide and confirm all questions with your care team.
Which input mode should I trust first?
Start with the most specific clinical record you have. IVF transfer and dated ultrasound usually override a rough LMP estimate because they anchor gestational age more tightly.
Why might two due-date tools disagree?
They may assume different cycle lengths, different embryo-age handling, or different rules for revising dates from ultrasound. Compare the same source date and method before interpreting the difference.
How should I use this result safely?
Use it for planning conversations, not medical decisions. Confirm anything that affects care, medication, or procedures with your clinician or maternity team.