Pregnancy Due Date Calculator (From Conception Date)
Use this pregnancy calculator by date of conception to estimate your due date, current gestational age, trimester, and key milestone dates.
Leave blank to use today’s date.
How this pregnancy calculator by date of conception works
This calculator uses a standard obstetric estimate: your due date is approximately 266 days (38 weeks) after conception. Most clinics track pregnancy by gestational age, which starts about two weeks before conception (from the last menstrual period). That is why many results also reference gestational weeks and days.
Core formula
- Estimated due date (EDD): Conception date + 266 days
- Estimated LMP: Conception date − 14 days
- Gestational age on a selected date: Days since conception + 14 days
What your results mean
After calculation, you will see:
- Estimated due date: Your projected delivery date based on known conception date.
- Current gestational age: Displayed in weeks and days in standard clinical format.
- Trimester: First, second, or third trimester based on gestational age.
- Days remaining or overdue: Time left until due date (or how far past due date you are).
- Milestone dates: Typical timing for testing, heartbeat detection windows, viability, and full term.
When a conception-date calculator is especially useful
A due date calculator by conception date can be more precise than an LMP-only calculator in specific cases, such as:
- Known ovulation timing from cycle tracking.
- Conception aligned with fertility monitoring methods.
- Assisted reproduction timelines (for example, known insemination or transfer schedules).
- Irregular cycles where LMP-based dating may be less reliable.
Even with exact conception tracking, ultrasound dating in early pregnancy is often used to confirm or adjust the estimated due date.
Pregnancy timeline overview (from conception)
Early weeks
- ~1 to 2 weeks after conception: possible positive home pregnancy test.
- ~5 weeks after conception: early cardiac activity may become detectable via ultrasound.
Middle phase
- ~18 to 22 gestational weeks: detailed anatomy scan window.
- ~24 gestational weeks: viability threshold discussions may begin in many regions.
Late pregnancy
- ~37 gestational weeks: early term begins.
- ~39 to 40 gestational weeks: full term and around due date period.
Why due dates sometimes change
Estimated due dates are exactly that—estimates. A full-term pregnancy can naturally vary, and only a small percentage of births occur on the precise due date. Your clinician may revise dates based on:
- First-trimester ultrasound measurements
- Cycle variability and ovulation uncertainty
- Fetal growth trends over time
- Medical factors affecting pregnancy course
Frequently asked questions
Is this calculator accurate?
It is mathematically accurate using the standard 266-day rule from conception. Clinical dating can still be adjusted after ultrasound review.
What if I only know my last period date?
Use an LMP-based due date calculator. This tool is best when conception date is known or closely estimated.
Can I use this if I conceived through fertility treatment?
Yes, this format is often helpful when timing is known. Still, always follow your fertility specialist’s official dating guidance.