Due Date Calculator
Calculate your pregnancy due date from your last menstrual period (LMP) or conception date. See key pregnancy milestones by trimester.
Estimated Due Date
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Key milestones
This calculator provides estimates only. Consult a healthcare provider for medical confirmation.
What is Due Date Calculator?
A due date calculator estimates when a baby is expected to be born based on the first day of the last menstrual period (LMP), a known conception date, or an IVF transfer date. A full-term pregnancy lasts approximately 40 weeks (280 days) from the LMP. The result is an estimated due date — most babies arrive within two weeks of this date.
How to use
- 1 Choose your input method: last menstrual period, conception date, or IVF transfer date.
- 2 Enter the relevant date using the date picker.
- 3 If using LMP, enter your cycle length — the default is 28 days.
- 4 The calculator displays your estimated due date and current week of pregnancy.
- 5 Review the key milestones table to see trimester boundaries, viability week, and full-term date.
Example calculation
If your last period started on March 1, with a 28-day cycle, your estimated due date is December 5 (280 days later). At 10 weeks pregnant you would be approaching the end of the first trimester on June 3. Viability at 24 weeks would fall around August 21.
Frequently asked questions
How accurate is an estimated due date?
Only about 5% of babies are born on their exact due date. Most arrive within 1 to 2 weeks before or after. The due date is best understood as the midpoint of a normal delivery window rather than a precise target.
What if my cycle is not 28 days?
Enter your actual cycle length in the cycle length field. The calculator adjusts the estimated ovulation day and due date accordingly. Shorter cycles shift the due date earlier; longer cycles shift it later.
Can I use conception date instead of LMP?
Yes. Switch to the Conception Date tab and enter when you believe conception occurred. This is particularly useful if you tracked ovulation and know the approximate date.
How does IVF dating work?
For IVF transfers, the calculator adds a fixed number of days to the transfer date based on embryo age. A Day 5 blastocyst transfer is treated as if conception occurred 17 days before the transfer date.
When should I see a doctor to confirm my due date?
An early ultrasound, typically at 8 to 12 weeks, is the most accurate way to confirm gestational age and due date. Always consult a healthcare provider for medical confirmation of your pregnancy timeline.