Pregnancy & Due Date Calculator Pro
Calculate your accurate estimated due date (EDD), track baby development week-by-week, view personalized milestones, and consult the built-in AI Pregnancy Advisor.
Pregnancy Trimester Road
You are currently in Trimester 1 (Weeks 1-13)Baby Size & Growth This Week
Week 4Your blastocyst has officially implanted in the uterine wall. The amniotic sac and placenta are rapidly developing!
Baby's Birth Profile & Fun Facts
Keepsake DetailsYour Personalized Pregnancy Milestone Schedule
Clinically estimated milestone dates computed specifically for your unique pregnancy cycle.
Smart Obstetric Advisor & Safety Copilot
Instant smart guidance on pregnancy food safety, trimester symptoms, and medical guidelines.
Select common pregnancy symptoms to view clinical cause, safe remedies, and warning red flags:
Hello mama! I am your clinical pregnancy assistant. Ask me anything about your current week, body changes, ultrasound tests, baby kicks, or prenatal vitamins!
Healthy Pregnancy Weight Gain Target
Based on Pre-Pregnancy Body Mass Index (BMI) • Institute of Medicine (IOM)Comprehensive Guide & Frequently Asked Questions
Everything you need to know about pregnancy calculations, accuracy of due dates, and clinical ultrasound scans.
How accurate is an estimated due date (EDD)?
Only approximately 4% to 5% of babies are born precisely on their estimated due date. Rather than a definite single day, think of your due date as a 5-week window: babies born anywhere between 37 weeks and 42 weeks are considered full term. The calculation provides a vital reference timeline for maternal care, scheduling prenatal genetic screenings, and monitoring fetal growth curves.
How does the Last Menstrual Period (LMP) method work?
The standard LMP calculation relies on Naegele's Rule: it adds 280 days (40 weeks) to the first day of your last normal period. Because ovulation typically occurs around day 14 of an average 28-day cycle, our calculator automatically adjusts for women with shorter or longer cycles by shifting the calculation by (Your Cycle Length - 28) days.
Why does an early ultrasound take precedence over the LMP date?
A first-trimester ultrasound measuring the crown-rump length (CRL) between 8 and 13 weeks has a margin of error of only ±3 to 5 days. If the ultrasound date differs from your LMP date by more than 7 days in the first trimester, American College of Obstetricians and Gynecologists (ACOG) guidelines recommend adjusting the official clinical due date to match the ultrasound.
How is an IVF embryo transfer due date calculated?
IVF due dates are extraordinarily accurate because the precise age of the embryo and the moment of implantation are documented. For a 5-day blastocyst transfer, 261 days are added to the transfer date. For a 3-day embryo transfer, 263 days are added. For an egg retrieval or IUI procedure, 266 days are added.
What are the three trimesters of pregnancy?
- First Trimester (Weeks 1 to 13): Rapid organogenesis, formation of neural tube, baby's heartbeat initiates, high hormonal surges (morning sickness).
- Second Trimester (Weeks 14 to 27): "The golden trimester" – energy improves, anatomy ultrasound scans, first fluttering baby kicks (quickening), gender determination.
- Third Trimester (Weeks 28 to 40+): Rapid baby weight gain, lung maturation, preparation for labor and delivery.
 |
| Pregnancy & Due Date Calculator |
Pregnancy & Due Date Calculator: Know Where You Are and When to Expect Your Baby One of the first questions after a positive pregnancy test is simple: when is the baby due? The answer also tells you which week you are in, which trimester you are in, and when your scans and tests should happen.
The Pregnancy & Due Date Calculator on this page works this out from a single date. Enter the first day of your last period, or your IVF transfer date, and you get your estimated due date, current gestational age and trimester.
Table of Contents
- What Is a Pregnancy and Due Date Calculator
- How to Use the Calculator
- How Your Due Date Is Calculated
- Adjusting for Your Cycle Length
- Due Date for IVF Pregnancies
- Why an Ultrasound Can Change Your Due Date
- Pregnancy Trimesters at a Glance
- Key Milestones and Checkups
- How Accurate Is a Due Date
- When to Speak to Your Doctor
- Frequently Asked Questions
What Is a Pregnancy and Due Date Calculator
It is an online tool that estimates your delivery date from the start of your pregnancy. It uses the standard method followed by doctors, which counts forward from the first day of your last menstrual period (LMP).
It also converts today’s date into gestational age, shown as weeks and days, so you can see exactly how far along you are.
How to Use the Calculator
- Choose your method: last menstrual period, conception date or IVF transfer.
- Enter the date. For LMP, use the first day of your last period, not the last day.
- Enter your average cycle length if it is not 28 days.
- Read the results: estimated due date, current week and day, trimester and key dates.
| Input | What to Enter | Note |
|---|---|---|
| Last period date | First day of your most recent period | Most commonly used method |
| Cycle length | Days from one period start to the next | Default is 28 days |
| Conception date | Date of ovulation or intercourse | Use only if LMP is unknown |
| IVF transfer date | Date of embryo transfer | Also select embryo day: 3 or 5 |
How Your Due Date Is Calculated
A full pregnancy is counted as 280 days, or 40 weeks, from the first day of the last menstrual period. This is about 266 days from conception, because ovulation usually happens around two weeks after the period starts.
The quick manual method is Naegele’s rule: subtract three months from your LMP date and add seven days.
| LMP Date | Calculation | Estimated Due Date |
|---|---|---|
| 1 January 2027 | Subtract 3 months, add 7 days | 8 October 2027 |
| 15 June 2027 | Subtract 3 months, add 7 days | 22 March 2028 |
Because months have different lengths, Naegele’s rule can differ from a straight 280-day count by a day or two in some cases. The calculator counts exact days.
Adjusting for Your Cycle Length
The 280-day rule assumes a 28-day cycle with ovulation on day 14. If your cycle is longer or shorter, ovulation shifts, and so does the due date.
| Your Cycle Length | Adjustment to Due Date |
|---|---|
| 24 days | Subtract 4 days |
| 28 days | No change |
| 32 days | Add 4 days |
| 35 days | Add 7 days |
If your cycles are very irregular, an LMP-based date may be unreliable. In that case, an early ultrasound is the better guide.
Due Date for IVF Pregnancies
IVF dates are more precise because the fertilisation or transfer date is known exactly.
| Method | Days Added to Get Due Date |
|---|---|
| Fresh IVF, from egg retrieval | 266 days |
| Frozen embryo, day 3, from transfer | 263 days |
| Frozen embryo, day 5 blastocyst, from transfer | 261 days |
Select the correct embryo day in the calculator, since a day 5 embryo has already developed for two more days than a day 3 embryo.
Why an Ultrasound Can Change Your Due Date
An early scan measures the baby’s crown-rump length, which is a reliable guide to age in the first trimester. Doctors compare the scan date with your LMP date.
| Stage of Pregnancy at Scan | Typical Rule |
|---|---|
| Up to about 9 weeks | Scan date is used if it differs from LMP by more than 5 days |
| About 9 to 14 weeks | Scan date is used if it differs by more than 7 days |
| After 20 weeks | Not used to redate, as baby sizes vary widely |
If the difference is smaller, your LMP-based date normally stays. Once your doctor confirms a due date, use that date in the calculator going forward.
Pregnancy Trimesters at a Glance
| Trimester | Weeks | What Generally Happens |
|---|---|---|
| First | Week 1 to 13 | Organs begin to form, early scans and blood tests |
| Second | Week 14 to 27 | Growth speeds up, baby movements are usually felt |
| Third | Week 28 to delivery | Weight gain, preparation for birth |
Doctors also use specific terms for delivery timing.
| Term | Gestational Age |
|---|---|
| Early term | 37 weeks to 38 weeks 6 days |
| Full term | 39 weeks to 40 weeks 6 days |
| Late term | 41 weeks to 41 weeks 6 days |
| Post term | 42 weeks and beyond |
Key Milestones and Checkups
The schedule below is a general guide. Your doctor will set a plan based on your health and risk factors.
| Approximate Week | Typical Event |
|---|---|
| 6 to 9 | First dating scan and confirmation of heartbeat |
| 11 to 14 | First trimester screening scan and blood tests |
| 18 to 22 | Detailed anatomy scan |
| 24 to 28 | Glucose test for gestational diabetes |
| 28 onward | More frequent visits and growth checks |
| 36 onward | Weekly visits and birth planning |
How Accurate Is a Due Date
A due date is an estimate, not a deadline. Only about 5 percent of babies arrive on the exact date. Most are born within a few weeks on either side of it.
Dates based on a regular cycle and an early scan are the most dependable. Dates based on a forgotten or uncertain LMP are the least dependable.
When to Speak to Your Doctor
The calculator cannot replace medical care. Contact your doctor promptly if you notice any of the following:
- Vaginal bleeding or fluid leakage
- Severe or persistent abdominal pain
- A sudden drop in baby movements in later pregnancy
- Severe headache, vision changes or sudden swelling
- Regular contractions before 37 weeks
If you have not yet had a scan, book a first appointment as soon as your pregnancy is confirmed.
Frequently Asked Questions
1. How is the due date calculated from the last period?
Doctors add 280 days, or 40 weeks, to the first day of your last menstrual period. The quick version is Naegele’s rule: subtract three months and add seven days. The calculator also lets you adjust for a cycle that is longer or shorter than 28 days.
2. Can my due date change after an ultrasound?
Yes. If an early scan shows a gap larger than 5 to 7 days from your LMP date, the doctor will usually switch to the scan date. Smaller gaps normally leave your original date unchanged. Once it is confirmed, use the confirmed date.
3. How many weeks pregnant am I if I just missed my period?
Pregnancy is counted from the first day of your last period, so a missed period usually means you are about 4 weeks pregnant. Conception itself happened roughly two weeks earlier.
4. Will my baby be born on the due date?
Most likely not. Only around 5 percent of births happen on the estimated date. Delivery anywhere from 37 to 42 weeks is considered within the normal range, and your doctor will advise you if the pregnancy goes beyond 41 weeks.
Disclaimer: This calculator gives an estimate for general information only and is not medical advice. Always confirm your due date and care plan with your doctor.
