Due Date Calculator
Calculate your estimated due date in 2 seconds. Full calendar: weeks pregnant, T1/T2/T3 ultrasounds, maternity leave and admin steps.
The standard average is 28 days.
Ideal if you've done IVF, IUI, or tracked your ovulation precisely.
This calculation uses today's date as a reference.
Enter your info on the left to see the result.
Your pregnancy timeline
Baby's side
Your key dates
Ultrasounds & Exams
- 1st Trimester Ultrasound
- 2nd Trimester Ultrasound
- 3rd Trimester Ultrasound
Admin & Retro-planning
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Pregnancy declaration Employer & Health insurance
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Daycare / Childcare Search for a nanny or daycare
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Hospital bag To be ready and stress-free
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Maternity leave Standard estimated start date
Indicative tool. Calculations do not replace medical advice.
Go deeper
Why this Due Date Calculator?
From the moment you learn you're pregnant, the first question is always the same: when will I give birth? The estimated due date (EDD) is the central reference of any pregnancy. It shapes your medical follow-up, administrative steps, childcare search and even maternity leave planning.
This calculator applies the modified Naegele's rule, the international reference method used by obstetricians: EDD = last period date + 280 days (with adjustment if your cycle differs from 28 days). It offers three calculation modes:
- From last menstrual period (LMP) — the most common mode from early pregnancy
- From conception date — ideal for IVF, IUI or tracked ovulation
- From current gestational age — useful after a dating ultrasound
How is the due date calculated?
A standard pregnancy lasts 40 weeks from the last menstrual period (LMP) — about 9 calendar months. The countdown always starts from the first day of your last period, not from conception.
If your cycle is longer or shorter than 28 days, the EDD is automatically adjusted: each day of difference shifts the date by one day. For example, a 35-day cycle pushes the EDD 7 days later.
Note on gestational weeks 📅
Gestational age (GA or SA in French) is the official count in France. Pregnancy starts at 0 weeks on the first day of your last period. Conception happens around week 2. The term is at 41 weeks. This differs from "real weeks of pregnancy" (which start at conception) — a difference of about 2 weeks.
Key steps at every stage
- T1Before 14 weeks — Declare your pregnancy
Register with your health insurance and employer to activate fully covered follow-up care. - T1From 12 weeks — Start childcare search
Public nurseries often have 1–2 year waiting lists. Starting early avoids unwanted surprises. - T211–13 weeks — Dating ultrasound (T1)
Confirms the EDD by biometric measurement and screens for Down syndrome. The ultrasound EDD is more accurate than the calculation. - T3Around 35 weeks — Hospital bag
Prepare it in advance: premature births are more common than expected. Ask your maternity hospital for their packing list. - W-66 weeks before term — Maternity leave
Standard prenatal leave starts 6 weeks before your EDD. Notify your employer and health insurer ahead of time.
FAQ
How accurate is the estimated due date calculation?
The EDD calculated from the last menstrual period is accurate to approximately ±2 weeks. This imprecision is normal because pregnancy duration varies naturally from person to person. The first trimester ultrasound (between 11 and 13 weeks) is far more accurate: it measures the embryo directly and can correct the EDD by a few days. In practice, only 5% of babies are born on their exact due date.
What is the difference between gestational weeks (SA) and real pregnancy weeks?
Gestational weeks (GW or SA in French) count from the first day of the last menstrual period, whereas "real weeks of pregnancy" start at conception. In practice, conception occurs about 2 weeks after the period, so a 12-week pregnancy (gestational) equals about 10 real weeks of pregnancy. All French healthcare professionals use gestational weeks — it is the official standard.
My cycle is not 28 days. How does that change the calculation?
The calculator automatically adjusts the EDD based on your cycle length. The rule is simple: 1 day difference from 28 days = 1 day shift in the EDD. For example, a 35-day cycle (+7) pushes the EDD back 7 days. A 21-day cycle (-7) brings it forward 7 days. The first trimester ultrasound remains the most reliable method for fine-tuning the date.
What is a post-term pregnancy?
A post-term pregnancy is when the pregnancy exceeds 41 weeks. In this case, intensive medical monitoring is implemented: fetal heart rate monitoring, amniotic fluid evaluation. Beyond 41+3 weeks, labor induction is generally offered by the medical team, as risks for the baby gradually increase. If your calculator shows the term has passed, consult your obstetrician or midwife.
At what gestational age can the EDD first be calculated?
You can calculate the EDD as soon as you know your last menstrual period date — even before you get a positive pregnancy test! The "current gestational age" mode is useful if you already know your stage of pregnancy from an ultrasound or blood test. The "conception" mode is ideal for IVF pregnancies, where the embryo transfer date is known with precision.
Is my pregnancy data stored anywhere?
No. All your data (dates, cycle length) is processed entirely in your browser and saved in your device's local storage (localStorage). No personal information is sent to a server. You can close the tab and find your dates when you return. Your data never leaves your device.
