A free due date calculator that also shows your pregnancy week, trimester and milestone dates.
Find your due date from your last period or conception date, and see your week, trimester and milestones.
Your numbers
The due date counts 280 days from the first day of your last period, the method ACOG describes. An early ultrasound gives the most accurate date.
Your result
Fill in the fields above to see your result.
These calculators give general estimates for healthy adults, not medical advice. Talk to your doctor before you change how you eat or train, especially if you're pregnant, take medication or have a health condition.
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This free due date calculator finds your estimated due date from the first day of your last period or a conception date, and shows how far along you are.
It gives your week and day, your trimester, the days to go, and the date of every milestone from the second trimester to full term.
I built it because the date math is simple once you know the rule, and the rule is the same one doctors start from.
Here's how a due date is worked out, a worked example, and why an ultrasound can change it. It's an estimate, not medical advice.
TL;DRKey takeaways
What is a due date calculator?
A due date calculator estimates when a baby is due from the start of the last period or the conception date.
It's also a pregnancy week calculator: from the same date, it shows how many weeks and days along you are today.
How a due date is worked out
The American College of Obstetricians and Gynecologists' Committee Opinion 700, reaffirmed in 2025, gives the rule: the estimated due date is 280 days after the first day of the last period.
Trimesters and term
ACOG splits pregnancy into 3 trimesters, and its Committee Opinion 579 names the weeks at term.
| Stage | Weeks |
|---|---|
| First trimester | Up to 13 weeks 6 days |
| Second trimester | 14 weeks 0 days to 27 weeks 6 days |
| Third trimester | 28 weeks 0 days on |
| Early term | 37 weeks 0 days to 38 weeks 6 days |
| Full term | 39 weeks 0 days to 40 weeks 6 days |
| Late term | 41 weeks 0 days to 41 weeks 6 days |
A worked example
Say the first day of the last period was January 1, 2026.
280 days later is October 8, 2026, the due date. The second trimester starts April 9 and the third July 16.
Why the date can change
The 280-day rule assumes a regular 28-day cycle. Cycles vary, and people don't always remember the exact date.
- Counting weeks from conception instead of from the last period
- Treating the due date as a fixed day rather than an estimate
- Skipping the early ultrasound that confirms the date
Who is the due date calculator for?
It's for anyone expecting or planning, and these tools help around it.
- Ovulation calculator – for your fertile days
- Water intake calculator – for how much to drink a day
- Sleep calculator – for bedtimes that end a full cycle
Share your dates with your doctor or midwife, who'll confirm them.
Plan your health with your AI
Take your numbers further in
Due Date Calculator FAQs
Questions about the due date calculator? Here's what to know.
A due date calculator estimates when a baby is due from the last period or the conception date, and shows how far along you are.
It's 280 days after the first day of the last period, the method ACOG describes.
Count the weeks from the first day of your last period, or let the calculator do it for any date.
Yes, add 266 days to the conception date.
At 14 weeks 0 days, by ACOG.
39 weeks 0 days to 40 weeks 6 days, by ACOG's definition.
An early ultrasound measures the pregnancy directly, which is more accurate than the date of the last period.
No, it's an estimate from the date of your last period or conception.
Yes, it's free with no sign-up.
It runs in your browser, and your numbers stay on your device.
I did.
I'm Navid Moazzez, and I made the due date calculator as one of my free tools on navid.me.
More about me.
Navid Moazzez
AI business strategist & AI OS builder
Navid Moazzez helps creators and founders master AI and build their own AI Operating System (AI OS) to automate their business and life.
Navid.me is reader-supported. When you buy through links on this site, I may earn an affiliate commission. Learn more.
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