Pregnancy Due Date Calculator
Estimate your due date and pregnancy week · free, no signup
Free Pregnancy Due Date Calculator — Estimated Due Date and Week
A pregnancy lasts about 40 weeks (280 days) counted from the first day of your last menstrual period (LMP). This calculator adds 280 days to your LMP — adjusted for the length of your cycle — to estimate your due date, following Naegele’s rule, the method most doctors use for a first estimate.
Enter the first day of your last period and your average cycle length and you will see your estimated due date, how many weeks and days pregnant you are today, which trimester you are in, and the dates of key milestones. Only about 4% of babies arrive on their due date, so treat the result as an estimate and follow your midwife’s or doctor’s guidance.
Key features
Estimated due date
Based on LMP and cycle length (Naegele’s rule).
Pregnancy week
Your current week and day, with trimester.
Key milestones
Dates for the end of each trimester and full term.
Countdown
Days left until your due date.
How to use it
- Enter the first day of your last period.
- Set your average cycle length (28 days by default).
- Read your due date and current week.
- Discuss the dates with your healthcare provider.
Worked example
Example
LMP 1 January 2026, 28-day cycle → due date 8 October 2026 Full term (37 weeks) begins 17 September 2026
Who uses this tool
Expectant parents
Get a first estimate and plan ahead.
Family and friends
Know roughly when to expect news.
Students and writers
Understand gestational timelines.
Tips for the best results
- An early ultrasound can give a more accurate date than LMP.
- If your cycle is longer or shorter than 28 days, adjust the cycle length.
- Term is considered 37–42 weeks.
- Keep antenatal appointments regardless of the estimate.
Common mistakes to avoid
- Treating the date as exact — most babies arrive within two weeks either side.
- Using the wrong first day (it is the first day of bleeding).
- Skipping medical care because a calculator says all is well.
Why use AZRS QuickFix?
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Frequently asked questions
How is a due date calculated?
Add 280 days (40 weeks) to the first day of your last period, adjusting for cycle length.
How accurate is it?
It is an estimate. Only about 4% of babies are born on their due date.
What if my cycle is not 28 days?
Enter your usual cycle length to adjust the estimate.
Which trimester am I in?
First trimester is weeks 1–13, second 14–27 and third 28 until birth.
Is this medical advice?
No. Always follow your doctor or midwife.
Is it free and private?
Yes, nothing is stored or sent anywhere.