Pregnancy Due Date Calculator

Estimate your due date, conception date, and trimester ends from your last period.

Days from one period to the next. 28 is typical.

Result—

Enter your values and calculate to see the result.

Formula used

due date     = LMP + 280 days + (cycle − 28)
conception   = LMP + (cycle − 14) days
1st trim end = LMP + 97 days
2nd trim end = LMP + 195 days
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Worked example

Last period 1 Jan 2026, 28-day cycle:

Due date = 1 Jan + 280 days = 8 Oct 2026

Conception ≈ 15 Jan 2026 (LMP + 14)

1st trimester ends ≈ 8 Apr 2026, 2nd ends ≈ 14 Jul 2026.

Frequently asked questions

How is the due date calculated?

Using Naegele's rule (280 days, 40 weeks) from the first day of your last menstrual period, adjusted by how much your cycle differs from 28 days.

My cycle is not 28 days. Does that matter?

Yes, slightly. Ovulation typically happens about 14 days before your next period, so a longer or shorter cycle shifts the due date. Enter your real cycle length and the calculator adjusts automatically.

How accurate is the due date?

Only about 1 in 20 babies arrives exactly on the due date. It is an estimate; an early ultrasound usually gives the most reliable gestational age.

What does the conception date estimate mean?

It is the approximate day of ovulation (about 14 days before your next period), which is when conception is most likely. It is an estimate, not a certainty.

When should I see a doctor?

As soon as you think you are pregnant. A clinician confirms the pregnancy and establishes gestational age with an ultrasound, which refines these estimates.