Free tools Pregnancy Due Date Calculator
Free tool · pregnancy week by week
Pregnancy Due Date Calculator: How Many Weeks Pregnant Am I?
Find your due date and exactly how many weeks and days pregnant you are, with your trimester, your month of pregnancy and the dates of your main scans and tests. Work it out from your last period, conception, IVF transfer, a scan, or a due date you already have. Nothing you type leaves your phone.
Important: an estimate only, not medical advice.
- For general information and education only: not medical advice, diagnosis or treatment.
- Results are estimates and may be wrong for your pregnancy. Do not use them to make medical decisions. Always confirm with your doctor, gynaecologist or midwife.
- Emergency? Bleeding, severe pain, leaking fluid or fewer baby movements: contact a doctor or hospital right away.
Parent Oven accepts no liability for decisions made using this tool. Last reviewed: 31 Oct 2026 · Sources
From the first day of one period to the first day of the next. Not sure? Leave it at 28.
Only if you know it, for example from ovulation tests. Sperm can live up to 5 days, so the date of sex is not always the date of conception.
Use the gestational age written on the scan report (for example 8w 3d). An early scan is the most accurate way to date a pregnancy.
See how many weeks you are today and your key dates.
Today is filled in. Change it to check any other day.
Nothing you type is saved or sent anywhere. It all stays on your phone.
How to use it
- Pick what you know. Most people use the first day of the last period (also called LMP). If your doctor already dated the pregnancy with a scan, use Scan or Due date instead.
- For the last period, set your usual cycle length. If your cycle is longer or shorter than 28 days, the calculator moves the due date by the difference.
- Tap Calculate. You get the due date, how far along you are today, the trimester and month, a progress bar to 40 weeks and a list of key dates with what is coming next.
- Want to know your week on another day, say for a scan appointment or a trip? Change Show my week on.
- Tap Add dates to my calendar to save the due date and the scan and test windows on your phone. The calendar file is made on your phone; nothing is sent to us.
How the due date is worked out
Doctors count pregnancy from the first day of the last period, not from conception. A pregnancy is 40 weeks (280 days) long when counted this way, and conception usually happens about two weeks in. That is why you can be “4 weeks pregnant” when the baby was conceived only 2 weeks ago.
| What you enter | How the due date is calculated |
|---|---|
| First day of last period (28-day cycle) | Period date + 280 days (Naegele’s rule) |
| First day of last period (other cycle length) | Period date + 280 days + (cycle length − 28) days |
| Conception date | Conception date + 266 days (38 weeks) |
| 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 |
| Scan date and the age on the report | Scan date − scan age + 280 days |
These are the methods described by the American College of Obstetricians and Gynecologists (ACOG). ACOG also says an ultrasound in the first trimester (up to 13 weeks 6 days) is the most accurate way to confirm or set the due date, and IVF dates are the most exact of all. So if your doctor gave you a date from an early scan, use that one.
Weeks, months and trimesters
“Weeks pregnant” is written as completed weeks and days: 12 weeks 3 days (12w 3d) means you are in your 13th week. The trimesters follow ACOG: the first trimester runs to 13 weeks 6 days, the second from 14 weeks to 27 weeks 6 days, and the third from 28 weeks until birth. Some apps start the third trimester at 27 weeks, so you may see a one-week difference.
In India, family will often ask “how many months?”. The calculator uses the same month table as our pregnancy weeks to months guide, where month 9 is week 36 to birth.
| Month | Weeks | Trimester |
|---|---|---|
| 1 | 1 to 4 | First |
| 2 | 5 to 8 | First |
| 3 | 9 to 13 | First |
| 4 | 14 to 17 | Second |
| 5 | 18 to 21 | Second |
| 6 | 22 to 26 | Second |
| 7 | 27 to 30 | Third |
| 8 | 31 to 35 | Third |
| 9 | 36 to 40+ | Third |
Your key dates explained
- NT scan, 11 weeks 0 days to 13 weeks 6 days. The first-trimester scan checks the baby’s heartbeat and growth, confirms the due date and measures the fluid at the back of the neck (nuchal translucency). It is often done with the double marker blood test as a screen for Down syndrome and other conditions. The window is narrow, so book it early (ISUOG guideline).
- Anomaly scan (TIFFA or level II scan), about 18 to 22 weeks. A detailed check of the baby’s body, heart, brain, placenta and fluid. The ISUOG guideline says it can be done between about 18 and 24 weeks depending on local law, so your doctor will pick the exact date.
- Glucose test for gestational diabetes. India’s national guidelines (MoHFW, 2018) say every pregnant woman should have a 75 g glucose test at her first antenatal visit and, if that is normal, again at 24 to 28 weeks.
- Td vaccine. Under India’s National Immunization Schedule, the first Td dose is given as early as possible in pregnancy and the second 4 weeks later (or one booster if you had two doses in a pregnancy within the last 3 years), per the MoHFW Routine Immunization Manual 2024.
- Early term (37 to 38 weeks), full term (39 to 40 weeks), late term (41 weeks), post-term (42 weeks and over). These are the ACOG definitions of term pregnancy. A baby born at 37 or 38 weeks is healthy in most cases, but the extra weeks in the womb help the brain and lungs.
The WHO recommends at least eight antenatal contacts during pregnancy, with the first one in the first 12 weeks. Book your first check-up as soon as you know you are pregnant.
When to call your doctor or go to hospital
- Bleeding from the vagina, a gush or trickle of fluid, or strong cramps or belly pain at any stage.
- A bad headache, blurred vision, sudden swelling of the face, hands or feet, or fits.
- Fever, burning when you pass urine, or vomiting so much you cannot keep fluids down.
- From about 28 weeks: your baby is moving less than usual, or you have regular tightenings before 37 weeks.
- You reach 41 weeks without labour starting. Your doctor will talk to you about monitoring and induction.
This calculator is for information only. It is not medical advice and cannot replace your doctor, midwife or ASHA worker. Always follow the dates and advice from your own antenatal care.
Sources
Official and primary sources only. Links were checked on 31 October 2026; any we could not open are marked.
- American College of Obstetricians and Gynecologists (ACOG). Committee Opinion 700: Methods for estimating the due date (2017). Used for: the due date formulas: first day of last period + 280 days, IVF transfer + 263 / 261 days, and why an early scan date is preferred. Note: the ACOG page shows the summary publicly; the full text is in Obstetrics & Gynecology 2017;129:e150–4.
- American College of Obstetricians and Gynecologists (ACOG). Committee Opinion 579: Definition of term pregnancy (2013). Used for: early term, full term, late term and post-term weeks.
- International Society of Ultrasound in Obstetrics and Gynecology (ISUOG). Practice Guidelines (updated): performance of the 11–14-week ultrasound scan (2023). Used for: the NT / first-trimester scan window.
- International Society of Ultrasound in Obstetrics and Gynecology (ISUOG). Practice Guidelines (updated): performance of the routine mid-trimester fetal ultrasound scan (2022). Used for: the anomaly (TIFFA) scan window.
- NHS (UK). 12-week scan (web page, checked Oct 2026). Used for: background on the dating scan (around 10 to 14 weeks).
- NHS (UK). 20-week scan (web page, checked Oct 2026). Used for: background on the anomaly scan (usually 18 to 21 weeks).
- Ministry of Health and Family Welfare, Government of India (MoHFW). National guidelines for diagnosis and management of gestational diabetes mellitus (2018). Used for: the glucose test at the first antenatal visit and again at 24 to 28 weeks.
- Ministry of Health and Family Welfare, Government of India (MoHFW). Routine Immunization Manual for Health Workers (2024). Used for: Td vaccine in pregnancy (Table 3.1). Note: blocks automated checks; opened normally in a browser on 31 Oct 2026.
- World Health Organization (WHO). WHO recommendations on antenatal care for a positive pregnancy experience (2016). Used for: the advice of at least eight antenatal contacts, the first in the first 12 weeks.
More for your pregnancy
- Pregnancy weeks to months and months to weeks
- Stages of pregnancy, trimester by trimester
- Simple steps for a healthy pregnancy
- Signs it is time to stop working during pregnancy
- How to tell your older child you are pregnant
- Pregnancy announcement captions
- Indian baby names with meanings
- Ovulation calculator
- Baby vaccination schedule with dates (India)
Questions
How accurate is a due date?
It is an estimate. Most babies are born in the two weeks before or after the due date, and only a few arrive on the day itself. An early scan or IVF dates make it more accurate than a period date, especially if your cycles are irregular.
My scan date is different from the period date. Which one is right?
Your doctor decides. ACOG advises changing the due date to the scan date when the difference is bigger than a set amount, which depends on how early the scan was (for example more than 5 days before 9 weeks, or more than 7 days from 9 to 13 weeks). If your doctor changed your date, choose Due date above and enter the new one.
I don’t remember my last period. Can I still use it?
Use the scan date and the age written on your first scan report instead, or the due date your doctor gave you. If you have not had a scan yet, see your doctor: a dating scan will give you a reliable date.
Does it work for twins?
The due date is calculated the same way, but twins are usually born earlier, often around 37 weeks or before. Your doctor will plan the birth with you.
Why does it say I conceived two weeks after my period?
That is an average for a 28-day cycle. Ovulation, and so conception, can happen earlier or later. If you used a different cycle length, the estimate moves with it.
Is anything saved?
No. The calculation runs on your phone or computer. Nothing is stored, sent to us or shared, and there is no sign-up.
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