Due date, weeks pregnant, and trimester dates.
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Uses of pregnancy due date
- Checking an estimated delivery date before a first prenatal visit.
- Seeing how a 32 day cycle moves 8 October 2026 to 12 October 2026.
- Finding the 14 and 28 week dates to plan around the second and third trimesters.
pregnancy due date pitfalls
- Leaving the cycle at 28 days when the real cycle is longer, so the due date lands early.
- Expecting the week count to jump when only the due date was adjusted.
- Typing the due date into the last-period field and reading the week count as if it were today.
pregnancy due date questions (8)
How many weeks pregnant am I?
Count whole days from the first day of your last period to the date you care about, then divide by 7. A last period on 1 January 2026 counted on 1 March 2026 is 59 days, which is 8 weeks and 3 days. Leave "Weeks pregnant on" blank to use today. The week count stays tied to the last period even when you change the cycle length.
What is the Naegele rule?
Add 280 days to the first day of the last period when the cycle is 28 days. That lands a 1 January 2026 period on 8 October 2026. 2026 is not a leap year, so the count does not pick up an extra February day. A 1 January 2024 period, in a leap year, lands on 7 October 2024 instead. The page uses that day count, not "plus one year, minus three months, plus seven days," because the month shortcut drifts at the ends of months.
What if my cycle is not 28 days?
Each day longer than 28 moves the due date one day later. Each day shorter moves it one day earlier. A 32 day cycle from 1 January 2026 is due 12 October 2026, four days after the 28 day date, and the note under the date says so. A 21 day cycle is due 1 October 2026, seven days earlier. At 28 the note stays hidden, because nothing moved. The weeks pregnant do not move with the cycle.
When do the trimesters start?
On this page the second trimester starts 98 days after the last period, which is 14 weeks, and the third starts at 196 days, which is 28 weeks. From 1 January 2026 those dates are 9 April 2026 and 16 July 2026. They follow the last period, not the shifted due date. A longer cycle does not slide the trimester dates.
What is the estimated conception date?
The page estimates conception as the cycle length minus 14 days after the last period. A 28 day cycle puts that on day 14, so 1 January 2026 gives 15 January 2026. A 32 day cycle gives 19 January 2026. The card says it is an estimate. It is not an ovulation test and it is not a scan.
Can I count a date that is already past the due date?
Yes. A last period on 1 January 2026 and a 28 day cycle, counted on 10 October 2026, is 2 days past the 8 October due date, and 40 weeks and 2 days pregnant, in the third trimester. The last period still has to be on or before the date you are counting from. A later period is an error, not a negative week count.
Does this replace a prenatal visit?
No. The page does date arithmetic so you can see a due date, a week count, and trimester dates change together. It does not read a scan, it does not diagnose a pregnancy, and it does not know a clinician has already dated the pregnancy a different way. If a scan date and this date disagree, the scan is the one to take to the visit. If cycles vary by more than a few days, or with PCOS, a calendar date can be off by a week or more; an ultrasound or a clinician gives a better date.
Are these dates uploaded?
No. The last period, the cycle length, and the count date stay in the browser. Runs entirely on your device. Nothing is uploaded.