How this Pregnancy Due Date Calculator works
Choose a dating method: first day of your last menstrual period (LMP) with optional cycle-length adjustment, a known conception date, IVF embryo transfer (day 3 or day 5), or ultrasound gestational age on a specific scan date. We apply standard clinical offsets (280 days from LMP, 266 from conception, IVF transfer formulas) to estimate your due date (EDD), current weeks and days pregnant, trimester, and key milestones.
Your report includes days until due, progress toward 40 weeks, estimated conception, trimester boundaries, milestone dates, insights, and PDF export. Early ultrasound often refines dating more than LMP alone—confirm with your prenatal clinician.
For cycle and conception planning, try our Fertility & Ovulation, PCOS Risk, or Water Intake calculators.
Disclaimer: Results are for informational purposes only and are not intended as medical advice, diagnosis, or treatment. See our disclaimer page.
Pregnancy Due Date Calculator
Estimate your pregnancy due date (EDD) and current gestational age from last menstrual period (LMP), conception date, IVF embryo transfer, or ultrasound measurements. Get trimester, milestone dates, days until due, progress toward 40 weeks, and PDF export—aligned with standard Naegele and clinical dating offsets.
Pregnancy dating
Adjusts EDD by (cycle − 28) days
Pregnancy Due Date Calculator – EDD, Gestational Age & Trimester Timeline
A pregnancy due date calculator estimates your expected delivery date (EDD) and how many weeks pregnant you are today. Most pregnancies are dated from the first day of the last menstrual period (LMP) using the 280-day (40-week) rule, but you can also enter conception date, IVF transfer details, or ultrasound gestational age. Our tool shows trimester, milestone dates, days until due, progress toward 40 weeks, dating formulas, screening insights, and PDF export—while reminding you that ultrasound and prenatal care refine the real timeline.
What Is Gestational Age & the Due Date?
Gestational age counts time from LMP (or an equivalent start date), not from the day you got a positive test. Estimated due date (EDD) is typically set at 40 weeks gestation. Ovulation and fertilization usually occur about two weeks after LMP in a 28-day cycle, which is why “12 weeks pregnant” means 12 weeks since LMP, not since conception.
1What You Enter
LMP method
- First day of last menstrual period
- Optional average cycle length (21–45 days)
Other methods
- Known conception date
- IVF transfer date + day 3 or day 5 embryo
- Ultrasound date + gestational weeks and days
2Formulas We Use
LMP (Naegele rule)
EDD ≈ LMP + 280 days (+ cycle length − 28)
Example: LMP Jan 1 → EDD around Oct 8 (40 weeks). 32-day cycle adds 4 days to the standard count.
Conception date
EDD ≈ conception + 266 days
Equivalent to 38 weeks from fertilization = 40 weeks gestational age from LMP.
IVF embryo transfer
Day 5: EDD ≈ transfer + 261 days · Day 3: transfer + 263 days
Accounts for embryo age at transfer in standard obstetric dating.
Ultrasound dating
LMP equivalent = scan date − (weeks×7 + days) → EDD = LMP + 280
Best when the scan was early in pregnancy; later scans are better for growth than initial dating.
3What Your Results Include
- Estimated due date (EDD) and days until due
- Current gestational age (weeks + days)
- Trimester label and trimester end dates
- Progress bar toward 40 weeks
- LMP equivalent and estimated conception date
- Pregnancy milestones (heartbeat, anatomy scan, viability, etc.)
- Screening insights, interpretation, and contributing factors
- Health considerations and prenatal recommendations
- Trimester and dating formula reference tables, PDF export / share
Trimester Timeline (From LMP)
| Trimester | Gestational weeks | Typical focus |
|---|---|---|
| First | 1 – 13+6 | Confirm pregnancy, folic acid, early labs, dating scan |
| Second | 14 – 27+6 | Anatomy scan, glucose screening, movement felt |
| Third | 28 – 40+ | Growth monitoring, birth planning, post-dates surveillance |
LMP vs Ultrasound vs IVF Dating
| Method | Best when | Limitation |
|---|---|---|
| LMP | Regular cycles, known period date | Irregular cycles, late ovulation |
| Ultrasound | Uncertain LMP, first trimester scan | Less accurate if scan is late |
| IVF | Known transfer date and embryo day | Clinic may use slight protocol variants |
Sample Due Date Calculations
Example A (LMP)
LMP March 1, 28-day cycle → EDD about December 6 (280 days). At 20 weeks from LMP you are halfway through the typical pregnancy calendar.
Example B (longer cycle)
LMP March 1, 32-day cycle → +4 days vs 28-day rule → EDD about December 10. Ultrasound in the first trimester can still fine-tune this.
Example C (IVF)
Day-5 transfer June 1 → EDD about February 17 (transfer + 261 days). Use clinic paperwork if their EDD differs by a day or two.
Benefits of Using This Pregnancy Due Date Calculator
- Multiple dating methods – LMP, conception, IVF, and ultrasound in one place.
- Cycle-length adjustment – Helpful when periods are not 28 days.
- Live gestational age – Weeks, days, and trimester today.
- Milestone timeline – Key prenatal landmarks with dates.
- Transparent formulas – Reference tables match clinical teaching.
- Holistic follow-up – Links to fertility, PCOS, water, and nutrition tools on this site.
How to Use This Pregnancy Due Date Calculator
- Pick your dating method – LMP is the default if you know your last period.
- Enter dates accurately – Use the first day of bleeding for LMP, not mid-cycle.
- Add cycle length – If your cycle is not 28 days.
- Calculate – Review EDD, gestational age, and milestones.
- Confirm at prenatal care – Bring results; early ultrasound may adjust EDD.
- Export or share – PDF for appointments or partner planning.
Key Prenatal Milestones (Typical Timing)
First trimester
Dating scan, folic acid, nausea management, genetic screening discussions per your clinician.
Second trimester
Anatomy scan (~18–22 weeks), glucose test, feeling fetal movement.
Third trimester
Growth checks, Group B strep testing, birth plan, monitoring if past due date.
Common Dating Mistakes
1. Using mid-cycle or positive-test date as LMP
LMP is the first day of menstrual bleeding, which shifts the entire timeline by about two weeks if confused with conception.
2. Ignoring irregular cycles
Long or short cycles change ovulation timing—enter cycle length or rely on early ultrasound.
3. Treating EDD as an exact birthday
Most births occur in a window around 40 weeks, not on a single calendar day.
4. Skipping prenatal care
A calculator cannot replace blood pressure checks, labs, or growth assessments.
The Science Behind Pregnancy Dating
Obstetric dating standardizes care worldwide using gestational age from LMP or ultrasound biometry. The 280-day rule dates to Naegele’s 19th-century formula; modern practice integrates first-trimester crown–rump length when LMP is uncertain. IVF dating adjusts for embryo development at transfer. Post-term surveillance and induction policies depend on accurate dating plus maternal and fetal risk factors—always individualized by your maternity team.
Related Tools on This Site
Pair dating with our Fertility & Ovulation Calculator, PCOS Risk Calculator, Water Intake Calculator, Protein Target Calculator, and Calorie Calculator for conception planning and pregnancy wellness context.
Medical disclaimer: This Pregnancy Due Date Calculator is for educational purposes only. It does not diagnose pregnancy complications, prescribe treatment, or replace obstetric care. Seek urgent care for heavy bleeding, severe abdominal pain, high fever, severe headache, vision changes, or reduced fetal movement.
Frequently Asked Questions (FAQs)
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