Summary: how to find your due date for free and privately
A pregnancy due date calculator estimates the date a baby is expected by counting 280 days (40 weeks) from the first day of the last menstrual period. Under Calculate from, choose Last period, Conception date or an IVF transfer, enter the date, and the results show your estimated due date, how far along you are today and the dates the second and third trimesters begin.
If your last period began on 1 January 2026 and your cycle is 28 days, the due date is 8 October 2026. Everything runs in your browser and nothing is uploaded (you can check the Network tab in DevTools). A due date is an estimate, not a medical record: your midwife or doctor may set a different one after an ultrasound.
Table of use: one pregnancy, four starting points
Four of the rows date the same pregnancy, one from each starting point. Each works back to the same equivalent first day of a last period (1 January 2026), so all four land on 8 October 2026. The second row shows how a 32-day cycle moves the due date four days later.
| Calculate from | You enter | Due date formula | Result |
|---|---|---|---|
| Last period | 1 Jan 2026, cycle 28 days | Date + 280 days | Thursday 8 Oct 2026 |
| Last period, longer cycle | 1 Jan 2026, cycle 32 days | Date + 280 + (32 − 28) days | Monday 12 Oct 2026 |
| Conception date | 15 Jan 2026 | Date + 266 days | Thursday 8 Oct 2026 |
| IVF (day-5 transfer) | Transfer on 20 Jan 2026 | Date + 261 days | Thursday 8 Oct 2026 |
| IVF (day-3 transfer) | Transfer on 18 Jan 2026 | Date + 263 days | Thursday 8 Oct 2026 |
The cycle adjustment lets a cycle other than 28 days move the date one day per day of difference. It accepts 20 to 45 days.
Features
- Four ways to start. Last period, conception date, or an IVF day-5 or day-3 embryo transfer, each with its own date label.
- Estimated due date with the weekday, and the range in which most babies arrive, two weeks either side.
- How Far Along and Days Until Due. Weeks and days today, the current week of pregnancy, and days remaining or days past due.
- Trimester badge and progress bar from Week 0 to Week 40.
- This stage note. A short description of what typically happens at your current week, with term definitions (early, full, late and post-term) that follow ACOG Committee Opinion 579.
- Important Dates: estimated conception, 14 weeks, 24 weeks, 28 weeks and full term at 39 weeks.
- Sanity checks. A date in the future is rejected, and a date that would put you more than 44 weeks along triggers a warning instead of a week count.
- Copy button that puts the key dates on your clipboard as plain text.
How to use the pregnancy due date calculator
- Under Calculate from, press the starting point you know: Last period, Conception date, IVF (day-5 transfer) or IVF (day-3 transfer).
- Pick the date in the box below it, for example First Day of Last Menstrual Period.
- For Last period, set Average Cycle Length (days) if it is not 28.
- Read Your Results: Estimated Due Date, How Far Along, Days Until Due and This stage. Scroll to Important Dates for trimester and term dates.
- Press Copy to save the dates, or change the date to compare scenarios.
Who can use it
Anyone expecting a baby can use it to get a first estimate before a booking appointment, and partners or relatives planning time off can use it to see the timeline. It is also useful if you know the conception date or IVF transfer date but not the last period. It does not replace a scan or advice from your midwife or doctor.
If you are still planning, the ovulation calculator estimates your fertile window. The date difference calculator counts days between any two dates, the countdown timer can count down to your due date, and the printable calendar generator makes a month to write appointments on. After the birth, the age calculator tracks your baby's age, and the weight converter and length converter switch measurements between pounds and kilograms or inches and centimetres. Browse the calculators hub, or read how we handle data in the privacy policy.
Frequently asked questions (FAQs)
How is a pregnancy due date calculated?
From your last period the calculator uses Naegele's rule: the first day of your last menstrual period plus 280 days (40 weeks). That assumes a 28-day cycle, so each day your cycle is longer or shorter moves the date one day later or earlier. From a conception date it adds 266 days; from an IVF transfer it adds 261 days (day-5 embryo) or 263 days (day-3 embryo).
How many weeks pregnant am I?
Enter your date and the How Far Along box shows your gestational age today in weeks and days, such as 35 weeks, 1 day, which means you are in week 36. It is counted from the first day of your last period, moved by the difference if your cycle is not 28 days, or from the equivalent date worked out from your conception or IVF transfer date.
How accurate is my due date?
It is an estimate. Only a small share of babies, around 4 to 5 percent, are born on their due date, and most arrive within two weeks either side of it. A first-trimester ultrasound is the reference method for dating a pregnancy, and your provider may change your due date if the scan differs from your period dates by more than about a week.
Why is pregnancy 40 weeks if conception happens about two weeks after my period?
Pregnancy is counted from the first day of your last period because that date is easier to know than the day of conception. Ovulation and conception usually happen about two weeks later, so the baby's actual age at the due date is roughly 38 weeks, even though the pregnancy is dated as 40.
How do I work out a due date from conception or IVF?
Choose Conception date, IVF (day-5 transfer) or IVF (day-3 transfer) under Calculate from, then enter that date. The calculator moves back to the equivalent first day of a last period: 14 days before conception, 19 before a day-5 transfer, 17 before a day-3 transfer. Then it adds 280 days. This also helps if you do not know your last period date.
When do the trimesters start?
The first trimester runs to the end of 13 weeks 6 days, the second from 14 weeks to 27 weeks 6 days, and the third starts at 28 weeks and lasts until birth. The Important Dates section lists the calendar dates the second and third trimesters begin for your pregnancy, along with 24 weeks and full term at 39 weeks.
Is it safe to enter my pregnancy dates here?
Yes. The calculator runs entirely in your browser, so the dates you enter are not uploaded, saved or shared, and they are gone when you close or reload the page. You can check this by opening the Network tab in your browser DevTools and confirming that nothing is sent while you change the inputs.
This page gives general information and estimates, not medical advice. Contact a midwife or doctor with questions about your pregnancy.