Pregnancy Due Date Calculator
Use this free pregnancy calculator to estimate your due date, current pregnancy week, and key milestones.
This calculator is for education only and does not replace medical advice from your OB/GYN or midwife.
How this pregnancy calculator works
This pregnancy calculator estimates your due date and gestational age using standard obstetric rules. Most due dates are estimated at 40 weeks (280 days) from the first day of your last period, even though conception usually happens about two weeks later.
You can use different inputs depending on what you know:
- LMP method: Best when you know the first day of your last period.
- Conception method: Useful when ovulation/conception date is known.
- Known due date: Works backward to estimate week of pregnancy and milestone dates.
Understanding your result
Estimated due date
Your due date is the best estimate of when labor may begin. Only a small percentage of births occur exactly on that date. A typical full-term delivery often happens between 37 and 42 weeks.
Gestational age (weeks and days)
Pregnancy age is usually shown as weeks + days (for example, 22 weeks and 3 days). Clinicians use this format for growth checks, ultrasound interpretation, and prenatal planning.
Trimester
- First trimester: Week 1 to 13
- Second trimester: Week 14 to 27
- Third trimester: Week 28 to birth
Why due date estimates can change
Pregnancy dating is an estimate, not an exact prediction. Your provider may adjust your due date if early ultrasound measurements differ significantly from menstrual dating. Common factors include:
- Irregular cycles
- Uncertain LMP date
- Late ovulation
- Early ultrasound findings
Common milestone dates you can track
Once your dates are calculated, many people like to track major checkpoints:
- End of first trimester
- 20-week anatomy scan window
- 24-week viability milestone (clinical context varies)
- Start of third trimester
- 39 weeks (full term period)
Tips for using a pregnancy week calculator
1) Use the most reliable date you have
If your cycle is regular and you remember your LMP clearly, start there. If not, conception date or a clinician-confirmed due date may be more accurate.
2) Keep expectations flexible
Due dates are guides for care planning, not fixed appointments. Labor timing naturally varies from person to person.
3) Confirm with prenatal care
Use online tools for planning, but always confirm timing for tests, scans, and appointments with your provider.
Frequently asked questions
Is this a conception calculator too?
Yes. If you enter LMP or due date, the tool estimates an approximate conception date. It remains an estimate because ovulation timing can vary.
Can I use this with IVF dates?
This page is designed for standard date-based estimation. IVF pregnancies are often dated with embryo transfer specifics by fertility clinics, so follow your clinic timeline first.
What if my result seems off?
Double-check date entry format and cycle length. If results still look unusual, your healthcare team can provide definitive dating based on medical history and ultrasound.
Final note
A pregnancy due date calculator is a practical planning tool for appointments, work leave discussions, and family preparation. For medical decisions, personalized recommendations from your obstetric provider should always come first.