Due date calculator
Find your due date and how far along you are from your last period, conception date or IVF transfer.
- ๐บ๐ธ US federal & state rules
- Naegele's rule, ACOG term definitions
- See sources
Estimated due date
Mon, Dec 7, 2026
33 weeks, 0 days pregnant as of Oct 19, 2026
- How far along
- 33 weeks, 0 days
- Trimester
- Third trimester
- Days to go
- 49 days
- Likely conception
- Mar 16, 2026
This is an example. Enter your numbers above and press the button to see your own result.
Key dates
| Second trimester starts (14 weeks) | Mon, Jun 8, 2026 |
|---|---|
| Third trimester starts (28 weeks) | Mon, Sep 14, 2026 |
| Early term starts (37 weeks) | Mon, Nov 16, 2026 |
| Full term starts (39 weeks) | Mon, Nov 30, 2026 |
| Due date (40 weeks) | Mon, Dec 7, 2026 |
| Late term starts (41 weeks) | Mon, Dec 14, 2026 |
| Postterm starts (42 weeks) | Mon, Dec 21, 2026 |
- This is an estimate from dates, not medical advice. Your doctor or midwife may move the due date after an early ultrasound, and that date is the one to go by.
- Few babies arrive on the due date itself. Most are born somewhere between 37 and 42 weeks.
Show the math
| First day of last period | Mon, Mar 2, 2026 |
|---|---|
| Cycle adjustment (28 - 28 days) | +0 days, so week 0 is Mon, Mar 2, 2026 |
| Due date = week 0 + 280 days | Mon, Dec 7, 2026 |
| 231 days since week 0, divided by 7 | 33 weeks, 0 days |
What to do next
How it works
Every method is turned into the same starting point, week 0 of pregnancy. From your last period, week 0 is the first day of that period, shifted by your cycle length minus 28 days. From a conception date, week 0 is 14 days earlier. From an IVF transfer, week 0 is the transfer date minus the embryo's age minus 14 days.
The due date is week 0 plus 280 days. How far along you are is the number of days since week 0, shown in weeks and days.
Things to keep in mind
This is an estimate from dates and not medical advice. An early ultrasound is often used to confirm or adjust the date, and your provider's date is the one that counts. Trimesters here are split at 14 and 28 weeks; some sources draw the lines a week earlier.
Sources
Rules applied as of 2026-10-19. See the sources below for details.
- ACOG Committee Opinion 579, Definition of Term PregnancyChecked 2026-10-19
- ACOG Committee Opinion 700, Methods for Estimating the Due DateChecked 2026-10-19
Frequently asked questions
How is a due date calculated?
The standard method, Naegele's rule, adds 280 days (40 weeks) to the first day of your last period. A period that started March 2, 2026 gives a due date of December 7, 2026.
What if my cycle is longer than 28 days?
The rule assumes ovulation on day 14 of a 28-day cycle. With a 32-day cycle you likely ovulated about 4 days later, so the due date moves 4 days later too.
How do I find my IVF due date?
Add 266 days to the transfer date, then subtract the embryo's age. A day 5 transfer adds 261 days and a day 3 transfer adds 263 days.
Why do weeks of pregnancy start before conception?
Pregnancy is counted from the first day of the last period, about two weeks before conception. So at conception you are already counted as about 2 weeks pregnant.
What do early term and full term mean?
ACOG calls 37 weeks 0 days to 38 weeks 6 days early term, 39 weeks to 40 weeks 6 days full term, 41 weeks late term and 42 weeks or more postterm.