Due Date Calculator
Estimate when your baby is due and how many weeks along you are today.
| Estimated due date | Sunday, July 18, 2027 |
|---|---|
| Estimated conception | Oct 25, 2026 |
| Pregnancy on Oct 11, 2026 | 0 weeks, 0 days |
| Trimester | First (weeks 1 to 13) |
| Days to go | 280 |
How to use it
- Choose what date you know and enter it.
- If you use your last period and your cycles aren't 28 days, enter your usual length; the date shifts by the difference.
- The due date from an early ultrasound is more accurate than any calculator; use what your provider gives you.
Formula
Due date = first day of last period + 280 days (40 weeks), + (cycle length − 28) daysFrom conception: + 266 daysIVF: day-5 transfer + 261 days; day-3 transfer + 263 daysWeeks pregnant = days since the first day of the last period ÷ 7
Example
If your last period started on January 1, 2026 and your cycle is 28 days, the estimated due date is Thursday, October 8, 2026, and conception was around January 15. On March 1, 2026 you would be 8 weeks, 3 days pregnant, with 221 days to go.
Questions
Why is pregnancy counted from my period, not conception?
By medical convention, pregnancy weeks start on the first day of the last period, about two weeks before conception in a 28-day cycle.
Why does the date differ from Naegele's rule?
Naegele's rule (subtract 3 months, add 1 year and 7 days) is a shortcut for 280 days and can land a day off around leap years or short months. This page counts the 280 days exactly.
How many babies arrive on the due date?
Only a small share. The due date is the middle of a normal range, and a term birth can come several weeks either side. This is an estimate, not medical advice.
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Last reviewed 2026-10-11. Found a mistake? Tell us.