Find out when your baby is expected to arrive. Choose from three calculation methods, last period, conception date, or IVF transfer, and get your estimated due date, current week, trimester timeline, and key milestones.
Pregnancy Due Date Calculator
Estimate when your baby will arrive
| Milestone | Date |
|---|---|
| Conception (estimated) | — |
| End of 1st Trimester | — |
| Gender can be determined | — |
| End of 2nd Trimester | — |
| Baby is viable | — |
| Full term begins | — |
| Due date | — |
Disclaimer: This calculator provides an estimated due date only. Only about 5% of babies are born on their exact due date. Most healthy deliveries occur between 37 and 42 weeks. Your healthcare provider will confirm your due date with an ultrasound. This tool is for informational purposes only and does not replace professional prenatal care.
How to Use This Calculator
Choose the method that matches the information you have.
Last Period is the most common starting point and what most doctors use. Select the first day your period started, not the last day of bleeding. If your cycles are longer or shorter than 28 days, adjust the dropdown. A 35-day cycle shifts your due date by a full week compared to a 28-day cycle.
Conception Date works if you were tracking ovulation. The calculator adds 266 days (38 weeks) from that date. Keep in mind that sperm can survive up to five days, so the date of intercourse and conception aren’t always the same.
IVF Transfer is for pregnancies conceived through in vitro fertilization. Select your transfer date and embryo type (Day 3 or Day 5). Because the embryo’s exact age is known from the lab, IVF due dates are typically the most precise.
How is a due date calculated?
Most calculations use Naegele’s Rule, a formula from 1806 that adds 280 days to the first day of your last period. It assumes a 28-day cycle with ovulation on day 14. Research shows an average discrepancy of 8–9 days compared to actual delivery dates. That margin shrinks when cycle length is accounted for.
The conception-based method adds 266 days from a known conception date, eliminating the guesswork about ovulation timing. IVF calculation is the most precise because the embryo’s exact age is known from the laboratory.
Your healthcare provider will likely confirm your due date with a first-trimester ultrasound (weeks 8–13), which is accurate to within 5–7 days.
How accurate is a due date?
A due date is an estimate, not a deadline. Only about 4–5% of babies arrive on their exact calculated date. Most healthy deliveries happen within two weeks before or after the estimate. Think of it as the center of a window, not a fixed target.
What do the results mean?
Current Week shows where you are in the 40-week timeline. Providers count from the last period, so “Week 1” is actually before conception — counterintuitive but universally standard.
Trimester tells you which phase you’re in. First trimester (weeks 1–12): major organs form. Second (weeks 13–26): energy returns, morning sickness fades. Third (weeks 27–40): baby gains weight and prepares for birth.
Progress Bar visualizes how far along you are as a percentage of the full 40 weeks.
What are the key pregnancy milestones?
End of 1st Trimester (~12 weeks): Major organ formation complete. Miscarriage risk drops significantly. Many parents share the news around this point.
Gender Determination (~18 weeks): The anatomy scan can typically identify the baby’s sex and checks structural development.
Baby Is Viable (~24 weeks): Premature babies have a meaningful chance of survival with intensive medical support. Survival rates are approximately 60–70% at well-equipped hospitals.
Full Term Begins (~37 weeks): Delivery is considered safe, though 39–40 weeks is the optimal window for lung, brain, and liver maturity.
Why your due date matters?
The entire framework of prenatal care is built around gestational age. Screening tests have specific timing windows — nuchal translucency between 11–14 weeks, anatomy scan at 18–22 weeks, glucose screening at 24–28 weeks. Getting these right depends on an accurate due date. The due date also helps providers assess whether a pregnancy is progressing normally and determines when induction conversations begin if pregnancy extends beyond 41 weeks.
Can my due date change?
Yes, but typically only once, early on. If a first-trimester ultrasound disagrees with the LMP estimate by more than 7 days, most providers adjust to match the ultrasound. Later ultrasounds aren’t used for re-dating because babies grow at individual rates after the first trimester.
What if my cycles are irregular?
Irregular cycles are one of the biggest sources of error in LMP-based calculations. If your cycles vary between 25 and 40 days month to month, ovulation timing is unpredictable. In this case, the conception date or IVF method will give a better estimate. If neither is available, early ultrasound dating is the most reliable fallback.
Do first-time pregnancies go longer?
Research suggests yes, by about 5 days on average compared to subsequent pregnancies. This calculator doesn’t adjust for birth order, but it’s worth keeping in mind if this is your first pregnancy and the due date passes without signs of labor.
What does "Full Term" actually mean?
The definition was updated in 2013:
Early Term: 37 to 38 weeks, 6 days. Generally safe, but babies benefit from staying in longer.
Full Term: 39 to 40 weeks, 6 days. The ideal window with the best health outcomes.
Late Term: 41 weeks to 41 weeks, 6 days. Normal range, but providers increase monitoring.
Post-Term: 42 weeks and beyond. Most providers recommend induction at this point.
Is it normal to go past my due date?
Very common. About 50–60% of pregnancies extend past the due date by at least a few days. Most providers let pregnancies continue until 41–42 weeks as long as monitoring shows everything is healthy. After 41 weeks, expect more frequent check-ups including non-stress tests and amniotic fluid checks.
How is the IVF due date different?
With IVF, the embryo’s exact age is known from the lab, eliminating the biggest source of error in other methods. A Day 5 blastocyst adds 261 days to the transfer date. A Day 3 embryo adds 263 days. This makes IVF due dates among the most reliable of any calculation method.
What this calculator can't account for
Every due date calculator works with population averages. Individual factors, maternal age, ethnicity, genetics, even the baby’s sex, can all influence when labor begins. Some families consistently carry pregnancies longer or shorter than 40 weeks. No formula captures all of these variables. This calculator provides an estimate; your healthcare provider will determine the most accurate date using your full clinical picture.
Frequently Asked Questions
How accurate is a due date calculator?
LMP-based calculators have an average margin of error of 8–9 days. Adjusting for cycle length helps. First-trimester ultrasound is more precise (within 5–7 days). IVF-based calculations are the most accurate because the embryo’s exact age is known.
Why does my doctor's due date differ from this calculator?
Doctors often adjust based on first-trimester ultrasound, especially if measurements disagree with the LMP estimate by more than 7 days. The ultrasound-adjusted date is usually more reliable.
Can my due date change during pregnancy?
Yes, but typically only once. If a first-trimester ultrasound shows a significant discrepancy, your provider will adjust it. Due dates are rarely changed after the first trimester.
What does "full term" mean?
Early term is 37–38 weeks. Full term is 39–40 weeks. Late term is 41 weeks. Post-term is 42+ weeks. Babies born at 39–40 weeks generally have the best outcomes.
Is it normal to deliver after my due date?
Very common. About 50–60% of pregnancies go past the due date. Most providers allow pregnancies to continue until 41–42 weeks without complications.
How does cycle length affect my due date?
A longer cycle means later ovulation, which pushes the due date later. A 35-day cycle shifts the date about 7 days compared to a 28-day cycle.
How is the IVF due date calculated differently?
A Day 5 embryo adds 261 days to the transfer date. A Day 3 embryo adds 263 days. The embryo’s known age eliminates the guesswork found in other methods.
Related Articles on DebugMD
- Prediabetes Symptoms: 9 Early Signs Most People Miss: Understanding blood sugar risk factors helps you prepare for the 24-week gestational diabetes screening.
- Signs of Iron Deficiency You Shouldn’t Ignore — Iron needs increase significantly during pregnancy. Catch deficiency early before it affects you or your baby.
- How to Stop Overthinking at Night: 7 Techniques: Sleep quality often drops during pregnancy, especially in the third trimester.
- How to Lower Cortisol Naturally: Stress management during pregnancy matters — chronic elevated cortisol can influence fetal development.
Disclaimer: This pregnancy due date calculator provides an estimate and should not replace professional prenatal care. Only about 5% of babies are born on their calculated due date. Your healthcare provider will confirm your due date through clinical examination and ultrasound. If you are pregnant or think you may be, please consult a qualified healthcare professional.
Health Tools & Calculators
Science-backed calculators and health assessments to help you understand your body, track your progress, and make informed decisions. All 100% free.