Pregnancy Due Date Calculator
Work out your estimated due date from the first day of your last period, your conception date or an IVF transfer date, and see exactly how far along you are.
Pregnancy timeline
| Milestone | Week | Date |
|---|
Week-by-week milestones
This calculator gives an estimate for information only and is not medical advice. Your doctor or midwife may adjust your due date after an ultrasound scan.
How to use the Pregnancy Due Date Calculator
- Choose a method: last period (most common), conception date, or IVF transfer.
- Enter the date. For the last-period method, also pick your usual cycle length (28 days if you're not sure).
- Read your due date along with how many weeks pregnant you are, your trimester and the number of days to go.
- Check the timeline and week-by-week milestones to see what's coming up next.
Due date formulas
| Method | Due date |
|---|---|
| Last menstrual period (28-day cycle) | First day of last period + 280 days |
| Last period, other cycle length | First day of last period + 280 days + (cycle length − 28) |
| Conception date | Conception + 266 days |
| IVF, day 3 embryo transfer | Transfer date + 263 days |
| IVF, day 5 embryo transfer | Transfer date + 261 days |
| IVF, day 6 embryo transfer | Transfer date + 260 days |
Example: if the first day of your last period was 1 March and your cycle is 28 days, your estimated due date is 280 days later, on 6 December.
Pregnancy trimesters
| Trimester | Weeks | Highlights |
|---|---|---|
| First | 1 to 13 | Organs begin to form, heartbeat visible on ultrasound, dating scan |
| Second | 14 to 27 | First movements, anatomy scan around 20 weeks, glucose test |
| Third | 28 to birth | Rapid growth, baby turns head-down, full term from 39 weeks |
Pregnancy weeks are counted from the first day of your last period, about two weeks before conception. That's why a pregnancy is said to last 40 weeks even though the baby develops for about 38.
Frequently asked questions
How is the due date calculated?
The standard method (Naegele's rule) adds 280 days, or 40 weeks, to the first day of your last menstrual period. If your cycle is longer or shorter than 28 days, the date is moved by the difference. From a known conception date the due date is 266 days later.
How do I calculate my due date after IVF?
Use the IVF tab and enter your embryo transfer date. For a day 5 blastocyst transfer the due date is 261 days after the transfer; for a day 3 transfer it's 263 days, and for day 6 it's 260 days.
How many weeks pregnant am I?
Pregnancy is counted from the first day of your last period, not from conception, so at conception you are already about 2 weeks pregnant. Enter your date and the calculator shows your exact weeks and days today.
When does each trimester start?
The first trimester runs from week 1 to the end of week 13, the second from week 14 to the end of week 27, and the third from week 28 until birth.
How accurate is a due date?
It's an estimate. Only about 4–5% of babies are born on their due date; most arrive between 37 and 42 weeks. An early ultrasound scan is the most accurate way to date a pregnancy, and your care provider may change your due date based on it.
Is this medical advice?
No. This calculator is for general information. Always follow the advice of your doctor or midwife.