Health & Wellness
Pregnancy Due Date Calculator
Estimate due date from LMP, conception, ultrasound, or IVF transfer. See gestational age, trimester timing, delivery window, and typical care milestones.
Plan your pregnancy timeline with multiple dating methods in one view. This calculator converts LMP, conception, ultrasound age, or IVF transfer into an estimated due date, gestational age, and delivery window. Track progress, key milestones, and care windows, then export a report for appointments, planning, and weekly checkins with confidence and clarity. Use it for planning conversations and calendar reminders.
Results
Pregnancy progress
Based on a 40-week (280-day) term.
Recommended due date
-
Summary
Key dates
Conception & implantation (approx.)
Implantation typically occurs about 6 to 10 days after ovulation.
Milestone dates (approx.)
Delivery window
Typical care windows
Method comparison
| Method | Due date | Delta vs recommended |
|---|
Recommendation prioritizes IVF dating, then ultrasound redating guidance, then LMP or conception.
Precautionary guidance
- Confirm the official due date with your clinician after early ultrasound.
- Irregular cycles or unknown LMP can shift dates; use ultrasound dating when available.
- Do not use these dates to self-diagnose or change medical care plans.
- Contact your care team with bleeding, severe pain, or concerning symptoms.
- Care windows are typical ranges and may shift based on clinical guidance.
Use this as a planning aid alongside clinical guidance.
These dates are planning estimates based on standard obstetric dating. Always confirm timing and care decisions with your clinician.
Medical disclaimer
This calculator is for education and planning only. It does not provide medical advice, diagnosis, or treatment.
- Actual due dates can shift after early ultrasound or clinician assessment.
- Cycle length, irregular ovulation, and medical history can change dating accuracy.
- Care windows shown here are typical ranges, not exact appointment dates.
Medical precautionary guidance
- Contact your care team for bleeding, severe pain, fever, or reduced fetal movement.
- Use clinician-confirmed dates for medical decisions, scheduling, or travel.
- Seek urgent care for symptoms that feel sudden, severe, or concerning.
How to use this calculator
Choose dating method
Start by selecting the method that best matches your available data. LMP works for regular cycles, conception is useful when the date is known, ultrasound is ideal when gestational age was measured, and IVF transfer is the most precise when embryo age and transfer date are known. Selecting the right method keeps the timeline aligned with clinical standards and reduces unnecessary date shifts later in pregnancy.
Enter baseline dates
Add the key date required by the chosen method, such as LMP date, conception date, ultrasound date, or transfer date. These dates anchor the due date calculation, so accuracy matters. If you have multiple dates, enter the most reliable option and use the method comparison table to see how other methods differ.
Add cycle details
If you use the LMP method, confirm the cycle length so the calculator can adjust ovulation timing. A longer or shorter cycle can move the due date by several days, which affects trimester timing and care windows. For ultrasound dating, enter weeks and days exactly as reported on the scan. These details make the gestational age estimate match your clinical records.
Set as-of date
Use the as-of date to see gestational age and time remaining on a specific day. This is useful for planning upcoming appointments or tracking progress week to week. You can set the date to today, a future appointment, or a past milestone to verify how the timeline looked then. The progress bar updates automatically based on this date so you can see how far along the pregnancy is in a 40-week term.
Review timeline outputs
After you calculate, review the due date, delivery window, trimester labels, and key milestones. Use the recommended due date and basis to understand which method is prioritized and why. The milestones and care windows provide typical timing for major scans and screening windows, helping you plan appointments and discussions. Use the method comparison table to see how each input method aligns with the recommendation.
Export share report
When you are ready to keep a record, export the report in PDF or spreadsheet format. The report includes inputs, results, milestones, care windows, and the method comparison table for clear documentation. Use the calendar PDF to add key dates to a planner or share with a care team. Recalculate anytime your clinician updates dating, and save the updated report to track changes consistently.
Advantages of this calculator
Multi method dating
The calculator supports LMP, conception, ultrasound, and IVF transfer dating in one place. This makes it easier to compare methods without switching tools or doing manual conversions. When you have multiple data points, you can see how each method shifts the due date and understand why clinicians may recommend one over another. This flexibility is especially helpful when cycles are irregular or when early scans provide new information.
Clear trimester mapping
Trimester boundaries are shown automatically based on the calculated due date. This helps you know which trimester you are currently in and when each stage ends. Having clear trimester mapping is useful for planning appointments, monitoring symptoms, and understanding typical care milestones. It also reduces confusion when different apps display trimester timing differently.
Milestone visibility
The calculator lists common milestone weeks, such as weeks 6, 8, 12, 20, and 28, which are often referenced in pregnancy care. Seeing these dates helps you plan discussions or schedule visits around key points. It also makes it easier to track progress week by week without counting manually. Milestone visibility keeps you oriented during longer timelines.
Care window planning
Typical care windows for screening and scans are mapped directly to your timeline. This saves time when you need to plan appointments or prepare for upcoming tests. Having the windows listed alongside your due date means you can align personal schedules with clinic availability. The windows are meant as planning ranges, so they can be adjusted based on clinician guidance.
Delivery range context
The delivery window section emphasizes that birth often occurs within a two-week range around the due date. This realistic framing helps reduce stress about a single day and supports better planning for work or travel. Seeing early, full, late, and post-term boundaries also clarifies how clinicians describe timing and why monitoring changes as the due date approaches.
Method comparison clarity
The method comparison table shows each dating method and its delta versus the recommended due date. This makes it easier to understand why a provider might adjust the date after ultrasound or IVF data. Clear comparisons also help you communicate with your care team and keep your personal tracking aligned with the official date used in your records.
Progress tracking support
The progress section shows days into pregnancy, days remaining, and a visual progress bar. This provides an at-a-glance view of how far along you are in the 40-week term. It helps with weekly check-ins and can be useful for planning milestones or preparing questions for appointments. Progress tracking also supports consistent updates if the dating basis changes.
Exportable documentation
The PDF and spreadsheet exports capture inputs, results, key dates, and care windows in a shareable format. This is helpful for keeping a personal record or sending a clear summary to a partner or clinician. The calendar PDF can be used to add events to planners or reminders. Exportable documentation keeps your planning consistent and reduces the need to re-enter dates elsewhere. You can archive reports by trimester, print them for visits, or share them with partners. Having a consistent format reduces manual note taking and keeps everyone aligned on dates, especially when schedules change or new ultrasounds update the plan over time.
Clinician aligned guidance
References and disclaimers keep the calculator aligned with clinical guidance and emphasize that results are for planning. This encourages users to confirm the official due date with their clinician and to treat care windows as typical ranges rather than guarantees. Clinician-aligned guidance supports safer decisions and helps users understand when to seek medical advice.
What this calculator includes
- LMP-based dating with cycle length adjustment.
- Conception date dating (38 weeks from conception).
- Ultrasound dating using gestational age on the scan date.
- IVF/FET transfer dating using embryo age at transfer.
- Gestational age, trimester timing, delivery window, and key care windows.
Global dating standards (summary)
- Standard obstetric dating counts 40 weeks (280 days) from the first day of the LMP.
- Conception dating counts 38 weeks (266 days) from conception or embryo transfer age.
- Early ultrasound is often used to confirm or adjust dates when the LMP is uncertain.
- IVF dating is precise because fertilization and transfer dates are known.
Dating adjustment guidance (ACOG summary)
- Before 9w0d: consider redating if ultrasound differs from LMP by more than 5 days.
- 9w0d to 13w6d: consider redating if difference is more than 7 days.
- 14w0d to 15w6d: consider redating if difference is more than 7 days.
- 16w0d to 21w6d: consider redating if difference is more than 10 days.
- 22w0d to 27w6d: consider redating if difference is more than 14 days.
- 28w0d and later: consider redating if difference is more than 21 days (use caution).
These thresholds are general guidance from ACOG. Clinicians use the full clinical context when confirming a final due date.
Typical care windows (weeks)
- Dating ultrasound: about 8 to 12 weeks.
- NT scan and screening: about 11 to 14 weeks.
- NIPT screening: often from 10 weeks and later.
- Anatomy scan: about 18 to 22 weeks.
- Glucose screening: about 24 to 28 weeks.
- Group B strep screening: about 36 to 37 weeks.
Term definitions (weeks)
- Preterm: before 37 weeks.
- Early term: 37w 0d to 38w 6d.
- Full term: 39w 0d to 40w 6d.
- Late term: 41w 0d to 41w 6d.
- Post-term: 42w 0d and later.
Accuracy and notes
- LMP dating assumes regular cycles and ovulation around cycle day 14.
- Irregular cycles, recent hormonal contraception, or unclear LMP can reduce accuracy.
- Early ultrasound is generally more accurate than later scans for dating.
- Most pregnancies deliver within a range, not on the exact due date.
When due dates change
Providers may adjust the due date if early ultrasound dating differs beyond a clinical threshold. Later in pregnancy, changes are less common because dating accuracy decreases as pregnancy advances.
- Confirm your official due date with your clinician after the first trimester scan.
- If dates shift, providers will update the care schedule and screening windows.
References (clinical guidance)
- ACOG: Methods for Estimating the Due Date
- ACOG: Definition of Term Pregnancy
- NHS: Due date and pregnancy dating
- NICE: Antenatal care guideline
- WHO: Antenatal care recommendations
Additional trusted resources
- CDC: Pregnancy
- NIH NICHD: Pregnancy
- MedlinePlus: Pregnancy
- Office on Women's Health: Pregnancy
- ACOG: Patient education (USA)
- RCOG: Patient information library
- NHS: Pregnancy guide
- NHS: Antenatal care and appointments (UK)
- NHS: Ultrasound scans in pregnancy (UK)
- March of Dimes: Pregnancy topics
- UNICEF: Pregnancy information
- SMFM: Maternal-Fetal Medicine patient resources
- SOGC: PregnancyInfo (Canada)
- RANZCOG: Royal Australian and New Zealand College of Obstetricians and Gynaecologists
- Australian Government: Pregnancy, Birth and Baby
- FIGO: International Federation of Gynecology and Obstetrics
Search topics covered
- pregnancy due date calculator
- gestational age calculator
- lmp due date
- conception date calculator
- ultrasound dating calculator
- ivf due date calculator
- embryo transfer due date
- trimester calendar
- pregnancy milestone dates
- delivery window
- dating ultrasound window
- pregnancy week calculator
- due date by cycle length
- ovulation conception estimate
- pregnancy care schedule
- estimated due date
Q&A
How is the due date calculated from the LMP?
The standard method adds 280 days (40 weeks) to the first day of the last menstrual period. If the cycle length differs from 28 days, the calculator adjusts by the difference.
Why does cycle length change the result?
Ovulation usually occurs about 14 days before the next period. Longer cycles shift ovulation later, and shorter cycles shift it earlier, so the due date is adjusted.
How is a due date calculated from conception?
Conception dating adds 266 days (38 weeks) to the conception date, which aligns with standard obstetric dating.
Is ultrasound dating more accurate than LMP?
Early ultrasound (typically in the first trimester) is often more accurate when LMP is uncertain. Later scans are less accurate for dating.
How does IVF dating work?
The due date is calculated from the embryo transfer date and the embryo age at transfer. Because the dates are known, this method is very precise.
What is gestational age?
Gestational age counts from the LMP, so it is usually about two weeks ahead of the conception date.
Why is there a delivery window instead of a single date?
Most pregnancies deliver within a range. A due date is an estimate, and normal delivery can occur weeks before or after.
Can my due date change later in pregnancy?
Providers may adjust the due date if early ultrasound dating differs beyond a clinical threshold. Later in pregnancy, changes are less common.
What if I do not know my LMP?
Use ultrasound dating or a known conception or IVF transfer date. These methods provide a more reliable estimate.
Does this calculator handle twins or multiples?
This tool uses standard singleton dating rules. Multiples often follow different monitoring schedules, so confirm timing with your clinician.
Why do different apps show different due dates?
Apps may use different assumptions for cycle length, rounding, or time zones. Ensure the same input method and dates when comparing.
Are milestone windows exact?
No. They are typical ranges used for planning. Your provider may recommend different timing based on your history and local practice.
What if my cycles are irregular?
Use ultrasound dating or consult your clinician to confirm gestational age.
When is the first trimester over?
It typically ends at 13 weeks and 6 days.
What is the difference between GA and fetal age?
Gestational age counts from LMP, about two weeks ahead of conception age.
Can I use this for frozen embryo transfer?
Yes. Choose the IVF/FET method and select embryo age at transfer.
Does time zone affect due dates?
Minor differences can occur if apps round differently; use the same inputs.