Free Tool
Due Date Calculator
A free due date calculator for every path to pregnancy. Enter your last period, conception date, or IVF transfer date and get your estimated due date in seconds.
I know my
This calculator provides an estimate. Your provider will confirm your due date, often after an early ultrasound.
How This Due Date Calculator Works
From your last period. This is Naegele's rule, the method most providers use: add 280 days (40 weeks) to the first day of your last menstrual period. It counts the two weeks before ovulation as part of the pregnancy, which is why you are “four weeks pregnant” the day your period is late.
From your conception date. If you know when you conceived, from ovulation tracking or a single possible date, the calculator adds 266 days (38 weeks). This skips the two-week assumption and is often a touch more precise.
From an IVF transfer. IVF dating is the most exact of all, because the embryo's age is known. The calculator adds 266 days to your transfer date and subtracts the embryo's age at transfer: 3 days for a Day 3 embryo, 5 days for a Day 5 blastocyst.
A note on cycle length. Naegele's rule assumes a 28-day cycle with ovulation on day 14. If your cycles are longer or shorter, your real due date shifts by roughly the same number of days, so a 32-day cycle means about four days later. If you track ovulation, use the conception date method instead. An early ultrasound may still move the date, and only about 4% of babies arrive on it, but most are born within two weeks either side.
How to Find Your Due Date in Three Steps
- 1
Choose Your Method
Pick last menstrual period, conception date, or IVF transfer, depending on which date you know most precisely.
- 2
Enter the Date
Add the first day of your last period, your conception date, or your transfer date. For IVF, choose whether it was a Day 3 or Day 5 embryo.
- 3
Read Your Results
See your estimated due date, how many weeks pregnant you are today, when each trimester starts, and your baby's zodiac birth chart.
What Happens Each Trimester?
First Trimester
Weeks 1 to 13. Your baby's organs form, and you may feel fatigue, nausea, and tenderness. This is a great time to find your prenatal provider.
Second Trimester
Weeks 14 to 27. Energy returns, you will feel movement, and the anatomy scan happens around week 20. Start thinking about your birth plan.
Third Trimester
Weeks 28 to 40+. Frequent appointments, nesting, and preparing your postpartum support. Make sure your team is assembled.
Due Date Calculator Questions
How is my due date calculated?
Most due dates are estimated using Naegele's rule: add 280 days (40 weeks) to the first day of your last menstrual period. If you know your conception date, we add 266 days (38 weeks). For IVF transfers, we count 266 days from the transfer date and subtract the embryo's age at transfer (3 or 5 days).
How accurate is a due date calculator?
About 4% of babies arrive on their estimated due date, but most are born within two weeks of it. Your provider may adjust your due date after an early ultrasound, which is the most accurate way to date a pregnancy in the first trimester.
What if my cycle is longer or shorter than 28 days?
Naegele's rule assumes ovulation on day 14 of a 28-day cycle. If your cycles run longer, ovulation likely happened later and your due date shifts later by the same number of days. Shorter cycles shift it earlier. If you track ovulation, the conception date method sidesteps the assumption entirely.
What are the three trimesters of pregnancy?
The first trimester covers weeks 1 to 13 (organ formation), the second trimester covers weeks 14 to 27 (movement and the anatomy scan), and the third trimester covers weeks 28 to 40 and beyond (nesting and preparing for birth).