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Pregnancy Due Date Calculator.

Calculate your estimated due date based on your last period

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Set your values

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Last Menstrual Period

Enter the first day of your last period. The estimate assumes a regular 28-day cycle and a 280-day pregnancy.

Note: This is an estimate, not a prediction. Only a small share of births happen on the estimated due date, and a healthcare provider can give a more accurate date from an ultrasound.
Estimated Due Date
July 4, 2027
280 days to go
Current Progress
0w 0d
Trimester
1st
Progress0%
Estimated Conception Date: ~10/11/2026
Time Elapsed: 0 weeks
Next Milestone: Entering the second trimester

FAQs

How is a due date calculated?

Most healthcare providers use the first day of your last menstrual period (LMP) and add 280 days (40 weeks) to estimate the due date. This is known as Naegele's rule.

How accurate is the due date?

An estimated due date is just that—an estimate. Only about 4% of babies are born on their actual due date. Most are born between 37 and 42 weeks.

What is my conception date?

Conception typically occurs about two weeks after the first day of your last period, assuming a 28-day cycle.

Cite this calculator

Canonical URL: https://mathify.one/fr/health/due-date

Cite as: Mathify. (2026). Calculateur de Date d'Accouchement. https://mathify.one/fr/health/due-date

Use Cases

Plan for your baby's arrival

Know your estimated due date to plan maternity leave, prepare the nursery, and schedule prenatal appointments.

Example: Enter your LMP to see your due date and current pregnancy week.

Track pregnancy progress

Monitor how far along you are and what to expect each week, helping you stay informed about your baby's development.

Example: At 20 weeks, you're halfway through your pregnancy.

Frequently Asked Questions

How is my due date calculated?
The calculator uses the first day of your last menstrual period (LMP) and adds 280 days (40 weeks) to estimate your due date. This is the standard Naegele's rule, assuming a regular 28-day cycle.
Can I find out my conception date?
Yes, the calculator estimates your conception date by subtracting 266 days (38 weeks) from your due date, which is the average time from conception to birth. This is an estimate, as conception can vary by a few days.
What if my cycle is irregular?
The calculator assumes a regular 28-day cycle. If your cycle is longer or shorter, your due date may differ. For the most accurate estimate, consult your healthcare provider, who may use ultrasound measurements.

Tips & Common Mistakes

Tips

  • Enter the first day of your last menstrual period accurately for the best estimate.
  • Remember that only about 5% of babies are born on their exact due date; it's normal to give birth a week or two before or after.
  • Use the conception date estimate to understand your pregnancy timeline, but rely on ultrasound for precise dating.
  • If your cycle is longer than 28 days, your due date may be later; consider discussing with your doctor.

Common Mistakes to Avoid

  • Using the date your period ended instead of the first day of your last period.
  • Assuming the due date is exact; it's an estimate and can change based on ultrasound findings.
  • Forgetting to account for irregular cycles, which can affect the accuracy of the calculation.

Last updated: August 13, 2026