Pregnancy Due Date Calculator

Last updated: Jul 22, 2026 | Reviewed by Calkulator Team | 2 min read

Health

Calculate your expected delivery date and pregnancy milestones

The due date is estimated at 280 days (40 weeks) from the first day of your last menstrual period, adjusted for cycle length. This calculator also shows key milestones — first heartbeat, anatomy scan, and viability dates.

Only 5% of babies arrive on the exact due date — consider it an estimate within a 2-week window.

LMP Details

Last Menstrual Period (LMP)

First day of your last menstrual period

Cycle Length (days)

Average menstrual cycle length (default 28 days)

Naegele's Rule

Due Date = LMP + 280 days (40 weeks)

Adjusted for non-28 day cycles: add or subtract the difference from 28 days.

Conception ≈ LMP + 14 days (ovulation)

Gestational Age = Days from LMP to today

Estimated Due Date

—

Current Week

—

Gestational Week

—

Trimester

—

Days Remaining

—

Conception Date

—

LMP + 14 days

Key Pregnancy Milestones

Milestone	Week	Estimated Date

Trimester Information

Trimester	Weeks	Key Events
First Trimester	0–13 weeks	Organ development, morning sickness
Second Trimester	14–26 weeks	Movement felt, anatomy scan
Third Trimester	27–40 weeks	Rapid growth, birth preparation

Live Result Illustration

Visual summary — updates instantly as you enter values above

LIVE

Real-Life Guide to Using the Pregnancy Due Date

Estimated delivery date (EDD). Use the examples and checks below to turn the number into a practical decision.

When this calculator is useful

Someone who just got a positive pregnancy test, or a couple actively trying to conceive, uses this to get a rough estimated delivery date to plan doctor visits, maternity leave, and milestones.

For most people, the best way to use the Pregnancy Due Date is to try the real case first, then change one input at a time. That makes the trade-off visible. For example, with a loan calculator you can change tenure while keeping the same rate; with an investment calculator you can change return assumption while keeping the same monthly contribution; with a health, education or measurement calculator you can check how much one input changes the final category.

The result should answer a practical question: Can I afford this? How much should I save? Is this score enough? Is this measurement within range? What is the safer or cheaper option? If the output does not answer the decision clearly, adjust the inputs until the scenario matches your real situation.

Real-Life Example

First-time mother estimating her EDD: A woman with a regular 28-day cycle recalls that the first day of her last menstrual period was 10 March.

1Naegele's rule: add 7 days to the LMP (10 March → 17 March), subtract 3 months (17 March → 17 December), giving an estimated due date of 17 December, which is equivalent to adding 280 days to the LMP.

2Now change one input, such as rate, time, quantity, unit or score, and compare the new result with the first one.

The due date is a calculated midpoint based on average cycle length, and actual delivery commonly falls anywhere within a couple of weeks either side of it.

Practical Advice

Use the Pregnancy Due Date as a planning tool, not just a number generator. Write down the inputs you used, because the final answer is meaningful only when you remember the assumptions behind it.

If the decision affects money, health, tax, safety, academics or legal compliance, keep a second check ready. That second check may be a bank quote, payslip, official rule, prescription, site measurement, mark sheet or invoice.

Common Mistakes

Assuming the due date is the exact day delivery will happen, when only about 5% of babies are actually born on their calculated due date
Entering the date of a missed period instead of the first day of the last menstrual period (LMP), which shifts the estimate by roughly a week
Using Naegele's rule as-is for an irregular cycle (say a 35-day cycle) without adjusting, since the rule assumes a standard 28-day cycle with ovulation on day 14
Ignoring that conception via IVF or a known ovulation date gives a more accurate estimate than LMP-based calculation, and mixing the two methods incorrectly
Treating the estimated due date as fixed once calculated instead of updating it after a first-trimester dating ultrasound, which is more accurate than LMP-based estimates

How to Interpret Results

The result is an estimated delivery date (EDD), not a guaranteed date; full-term delivery is considered anywhere from 37 to 42 weeks of pregnancy, so treat the number as the center of a several-week window and confirm timing with your obstetrician's ultrasound dating.

A good interpretation looks at both the main result and the supporting values. If a page shows totals, ratios, categories, schedules or warnings, read those together instead of focusing only on the biggest number.

Pregnancy Due Date FAQs

Useful answers for interpreting the output, avoiding mistakes and using the result responsibly.

How does this calculator estimate the due date?

It typically uses Naegele's rule, which adds one year, subtracts three months, and adds seven days to the first day of your last menstrual period, equivalent to adding 280 days (40 weeks). This assumes a standard 28-day cycle with ovulation around day 14.

What if my menstrual cycle is longer or shorter than 28 days?

Naegele's rule becomes less accurate for irregular or unusually long/short cycles, since ovulation may not fall on day 14. Some calculators let you input average cycle length to adjust the estimate, and a doctor can refine this further with an early ultrasound.

Is the due date the exact day my baby will be born?

No, it is a statistical estimate, and only a small percentage of babies arrive exactly on their calculated due date. Delivery anywhere from 37 to 42 weeks of pregnancy is considered full term and normal.

Is an ultrasound more accurate than this calculator?

Yes, a dating ultrasound performed in the first trimester, especially between 8-13 weeks, is generally considered more accurate than LMP-based calculation because it measures the fetus directly rather than relying on cycle assumptions. Your doctor may adjust your due date after this scan.

Can I use this if I conceived through IVF?

LMP-based calculators are less relevant for IVF pregnancies since the exact fertilization or transfer date is already known. Your fertility clinic typically provides a due date calculated directly from the embryo transfer date, which is more precise than this general calculator.

What should I do immediately after getting an estimated due date?

Use it as a rough planning guide to schedule your first prenatal visit, ideally within the first trimester, where a doctor will confirm dating and check on the pregnancy's progress. This calculator is not a substitute for that first medical consultation.

Does this calculator confirm that I am actually pregnant?

No, this tool only estimates a due date assuming pregnancy is confirmed by a test or doctor; it does not diagnose pregnancy itself. A home pregnancy test followed by a doctor's confirmation is the appropriate next step if you have not already had one.

Why did my doctor give me a different due date than this calculator?

Doctors often revise the estimate after an ultrasound measures the fetus's size, which can be more reliable than LMP-based calculation, particularly if your cycle is irregular or you are unsure of the exact LMP date. Always follow your doctor's updated date over a calculator estimate.

What is a Pregnancy Due Date Calculator?

The Estimated Due Date (EDD) is calculated using Naegele's Rule: add 40 weeks (280 days) to the first day of your Last Menstrual Period (LMP). This assumes a regular 28-day cycle — cycles longer or shorter than 28 days can shift the due date by a few days.

Beyond the due date, this calculator maps your full pregnancy journey — current gestational week, which trimester you're in, key milestone dates (12-week scan, 20-week anomaly scan, 28-week glucose test), and days remaining until delivery.

Example Calculation

Scenario: Mrs. Priya Sharma, 29-year-old teacher from Nagpur — Last Menstrual Period (LMP) started on 10 February 2025, regular 28-day cycle

1EDD = LMP + 280 days = 10 Feb 2025 + 280 days = 17 November 2025

2As of 20 May 2025 → Gestational age = 14 weeks 3 days (2nd trimester)

3Key upcoming milestones: Anomaly scan around 1 July 2025 (20 weeks), glucose test around 22 July 2025

✓ Result: Priya's due date is 17 November 2025. She is currently 14 weeks + 3 days pregnant (2nd trimester).

How to Use the Pregnancy Due Date Calculator

Enter the date of the first day of your Last Menstrual Period (LMP) — this is the standard medical starting point for all pregnancy dating.
Enter your average menstrual cycle length in days — the default is 28 days; adjust if your cycle is regularly longer or shorter than this.
Click "Calculate Due Date" — Naegele's Rule adds 280 days (40 weeks) to your LMP, adjusted for your cycle length, to compute the Estimated Due Date (EDD).
Review the gestational age (current week and day), trimester, days remaining until due date, and approximate conception date.
Check the Key Pregnancy Milestones table for important dates — nuchal scan (11–13 weeks), anomaly scan (18–20 weeks), glucose test (24–28 weeks), and more.

Benefits

Uses Naegele's Rule — the same method employed by OBGYN doctors worldwide for EDD estimation
Adjusts for non-28-day cycles — longer cycles shift due date forward, shorter cycles back
Trimester classification shown instantly: First (0–13 weeks), Second (14–26 weeks), Third (27–40 weeks)
Key antenatal milestone dates pre-calculated — plan NT scan, anomaly scan, and GCT appointments
Conception date estimated at LMP + 14 days — helpful for correlating with early ultrasound CRL findings

Key Terms

LMP: Last Menstrual Period — the first day of your most recent period; standard reference point for pregnancy dating
EDD: Estimated Due Date = LMP + 280 days (40 weeks); actual delivery typically occurs within 2 weeks before or after
Gestational Age: Number of weeks and days counted from LMP — not from the actual conception date (always 2 weeks ahead of fetal age)
Naegele's Rule: EDD = LMP + 9 months + 7 days (or LMP + 40 weeks); standard since 1830; assumes 28-day cycle
Trimesters: First: weeks 0–13 (organ development); Second: weeks 14–26 (anatomy scan); Third: weeks 27–40 (growth and birth prep)

Frequently Asked Questions

How accurate is this pregnancy due date calculator?

This calculator uses Naegele's Rule — the standard medical method — which assumes a 28-day cycle and ovulation at day 14. Only about 5% of babies are born on the exact due date; most deliveries occur within 2 weeks before or after. Accuracy improves with ultrasound dating using Crown-Rump Length (CRL) measurement in the first trimester (8–10 weeks), because it directly measures embryo size rather than relying on LMP recall. Your OBGYN will confirm and may revise the EDD after the first scan.

What if my menstrual cycle is not 28 days?

The calculator adjusts for non-28-day cycles. For a 35-day cycle (7 days longer than standard), the EDD shifts forward by 7 days. For a 21-day cycle (7 days shorter), EDD moves back by 7 days. Adjustment formula: EDD = LMP + 280 + (Cycle Length − 28) days. If your cycle is irregular or you're unsure of your LMP, first-trimester ultrasound dating (CRL measurement) is the most reliable method for establishing gestational age.

What is the difference between gestational age and fetal age?

Gestational age is counted from LMP — at "12 weeks pregnant," the gestational age is 12 weeks, but the fetus is only about 10 weeks old (fetal age). This 2-week difference exists because LMP typically precedes ovulation (and conception) by approximately 14 days. All medical literature, pregnancy apps, and this calculator use gestational age as the standard measurement — so when your doctor says "12 weeks pregnant," they always mean 12 weeks from LMP.

What are the key antenatal scans and tests in India?

Standard antenatal schedule in India: NT (Nuchal Translucency) scan at 11–14 weeks gestational age — screens for chromosomal abnormalities; Anomaly Scan at 18–20 weeks — checks all fetal organs; Growth Scan at 28–32 weeks; Final scan at 36–37 weeks for fetal position and delivery planning. Blood tests: Dual Marker (11–13 weeks), Quad Marker (15–20 weeks), GCT/OGTT Glucose Challenge (24–28 weeks). All dates align with gestational age from your EDD — the milestones table in this calculator is based on these standard timelines.

Is it normal for delivery to happen before or after the due date?

Yes, completely normal. Only about 5% of babies are born on the exact EDD. Roughly 80% of deliveries occur within 2 weeks of the due date — the "term" window is 37–42 weeks. Deliveries before 37 weeks are preterm; after 42 weeks are post-term. If labour does not start by 41 weeks, your OBGYN may discuss induction options. Plan a 2-week window around your EDD for practical arrangements — hospital bag, maternity leave start date, and childcare planning.