Due date calculator: when is my baby due?
Estimated due date: Thursday, June 3, 2027
About 8 weeks 4 days today. Only around 4% of babies arrive on their due date; your midwife or doctor will confirm it with a scan.
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Your estimated due date is 280 days (40 weeks) after the first day of your last period, assuming a 28-day cycle. If your cycles are longer or shorter, the date shifts by the same number of days. Enter your last period and cycle length above to see your due date and how many weeks pregnant you are today. A dating scan confirms it.
How the due date is calculated
Doctors and midwives date pregnancy from the first day of your last menstrual period (LMP), not from the day you conceived. That's why you're already counted as about two weeks pregnant at conception. The classic method, called Naegele's rule, adds 280 days to your LMP.
That rule assumes ovulation on day 14 of a 28-day cycle. The calculator adjusts for your own cycle length: with a 32-day cycle you probably ovulated about four days later, so your due date moves four days later too.
| Last period started | Cycle length | Estimated due date |
|---|---|---|
| 1 March | 28 days | 6 December |
| 1 March | 32 days | 10 December |
| 1 March | 25 days | 3 December |
Calculated in your browser, nothing stored. If you don't remember your last period, or your cycles are irregular, your scan date will be more accurate.
How accurate is a due date?
It's an estimate in the middle of a range. A full-term pregnancy lasts anywhere from 37 to 42 weeks, and only about 4 to 5% of babies arrive on their due date. ACOG advises that a first-trimester ultrasound is the most accurate way to date a pregnancy, and your midwife or doctor may update your due date after it. In the UK, the NHS offers a dating scan at around 12 weeks.
- Your LMP date is a guess? Use your best estimate, then trust the scan.
- Conceived through IVF? The transfer date gives a more exact due date than the LMP.
- Irregular cycles or recently off the pill? Ovulation timing is uncertain, so the scan matters more.
Pregnancy by trimester
| Trimester | Weeks | What usually happens |
|---|---|---|
| First | 1 to 13 | Missed period, positive test, nausea, tiredness, sore breasts, dating scan |
| Second | 14 to 27 | Energy often returns, the bump shows, first movements around 16 to 24 weeks, anatomy scan |
| Third | 28 to 40+ | Growth, more discomfort and broken sleep, preparing for birth |
Mood in pregnancy and after
Hormones rise far higher in pregnancy than in any menstrual cycle, and mood often changes with them: teariness, worry and irritability are common, especially in the first trimester. If you've had strong PMS or PMDD, mention it to your midwife, as it can be linked to a higher chance of mood problems around pregnancy. After birth, see our guide to postpartum mood and your returning cycle and your period after pregnancy.
Lulu doesn't follow pregnancy week by week. It helps before and after: knowing when your period was due, and tracking your cycle and mood as they return after birth.
When to get medical help
Book in with a midwife or doctor as soon as you know you're pregnant. Get urgent help for heavy bleeding, severe belly pain, one-sided pain with a positive test, a severe headache with vision changes, or if your baby moves less than usual later in pregnancy.
Frequently asked questions
How is my due date calculated?
By adding 280 days (40 weeks) to the first day of your last period, adjusted for your cycle length.
Why am I two weeks pregnant at conception?
Because pregnancy is counted from the start of your last period, about two weeks before ovulation in a 28-day cycle.
Can my due date change?
Yes. Your midwife or doctor may update it after your dating scan, which is more accurate than the period date.
When should I take a pregnancy test?
From the first day of your missed period. Our pregnancy test calculator shows your date.
Sources
- ACOG: Methods for Estimating the Due Date (Committee Opinion 700)
- NHS: Due date calculator
- NHS: Signs and symptoms of pregnancy
This page is for information only and isn’t medical advice. If something worries you, please talk to a doctor.
Keep reading
When to take a pregnancy test: find your most accurate dayWhen to take a pregnancy test: enter your last period and cycle length to see the earliest testing day and the day a result is most reliable.
Implantation calculator: when does implantation happen?Free implantation calculator: see the days implantation would most likely happen this cycle, what implantation bleeding looks like, and when to test.
Your period after pregnancy: when it comes back and what changesYour period after pregnancy: when it usually returns with and without breastfeeding, why ovulation comes first, what first periods feel like, and red flags.When should you take a pregnancy test?How soon can you take a pregnancy test? Most work from the first day of a missed period. When early tests work, best time of day, and when to test again.
Ovulation calculator: when do I ovulate?Free ovulation calculator: enter your last period and cycle length to see your likely ovulation day for the next 4 cycles. Private, instant, estimates only.