Pregnancy Due Date Calculator
Estimate your due date from the last menstrual period (Naegele's rule, any cycle length), conception date or IVF transfer, with gestational age and trimester.
Fill in the fields above to see the result.
- Naegele's rule: due date = first day of last period + 280 days, adjusted by (cycle length − 28). Conception + 266 days; IVF day-3 transfer + 263, day-5 transfer + 261.
- An estimate for information only, not medical advice. Your doctor or midwife may date the pregnancy by ultrasound.
What is Pregnancy Due Date Calculator?
Estimates the due date from the first day of your last period (adjusted for cycle length), a known conception date or an IVF embryo transfer date. It also shows how far along the pregnancy is on a chosen date, the trimester, days remaining, the estimated conception date and key milestones.
How to use Pregnancy Due Date Calculator
- Choose the Method: last period, conception date or IVF transfer (day-3 or day-5 embryo).
- Enter the date and, for the last-period method, your average Cycle length.
- Optionally change As of date (today by default) and read the due date, gestational age and milestones.
Example
Last period 2026-01-01, 28-day cycle, as of 2026-03-01
Due date October 8, 2026; gestational age 8 weeks 3 days; 1st trimester
When to use Pregnancy Due Date Calculator
Use it for an early estimate and planning. Only about 4–5% of babies are born on the due date itself, and an early ultrasound often adjusts the dating. This is information, not medical advice.
How Pregnancy Due Date Calculator works
Naegele's rule: due date = first day of the last menstrual period + 280 days, plus (cycle length − 28) days for longer or shorter cycles. From conception: + 266 days. IVF: day-3 transfer + 263 days, day-5 transfer + 261 days. Gestational age = as-of date − (due date − 280 days), shown in weeks and days; the 1st trimester runs to 13 weeks 6 days and the 2nd to 27 weeks 6 days. Dates are calculated as calendar days without time zones.
Common Use Cases
- Estimating the due date after a positive test
- Knowing how many weeks pregnant you are
- Planning leave and appointments
- Checking an IVF clinic's date
FAQs
Why is pregnancy counted from the last period?
Ovulation is rarely known exactly, while the first day of the last period usually is. Gestational age therefore includes about two weeks before conception.
My cycle is 32 days – does that matter?
Yes. Longer cycles usually mean later ovulation, so the due date moves 4 days later for a 32-day cycle.
Which date should I trust, this or the ultrasound?
An early ultrasound is generally more accurate; follow the date your doctor or midwife gives you.