Open the Pregnancy Due Date Calculator
Estimate your baby's due date from your last period or conception date. See your current week, trimester, key milestones and a countdown.
- Free to use
- No signup
- Nothing to install
- Runs in your browser
Illustration. Open the tool for the real thing.
What is the Pregnancy Due Date Calculator?
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.
3 steps to your result
Open the tool and follow along. Nothing to install.
What you get
Based on LMP and cycle length (Naegele’s rule).
Your current week and day, with trimester.
Dates for the end of each trimester and full term.
Days left until your due date.
AZRS tools are free to open and use.
It opens in your browser, so there is nothing to download.
Used for
Pick one to see how it fits.
How it compares
A plain look at this tool next to the usual alternative.
| This calculator | Desktop software | |
|---|---|---|
| Install | Nothing to install | Usually an app or program to install |
| Account | No signup | Depends on the product |
| Cost | Free to use | Free or paid, depends on the product |
| Where it runs | In your browser tab | On your computer |
Questions people ask
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.
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