Use the pregnancy due date calculator above to estimate your due date using three clinically validated methods — LMP date, conception date, or IVF transfer date. Whether you just found out you are pregnant, are tracking your progress week by week, or need to calculate a due date for an IVF pregnancy, this free online pregnancy due date calculator gives you a complete pregnancy timeline including your estimated due date, current week and day, trimester, days remaining, a visual progress bar, a trimester chart, and all major pregnancy milestones from the first trimester through full term. Choose the method that fits your situation, enter your dates, and click “Calculate Due Date” for instant, medically accurate results.
Below you will find a complete step‑by‑step guide on how to use all three calculation methods, detailed explanations of how each formula works, trimester breakdowns, pregnancy milestones, and answers to frequently asked questions.
How to Use the Pregnancy Due Date Calculator
The pregnancy due date calculator features three calculation tabs designed for different situations. Choose the method that best matches what information you have available:
Tab 1: LMP Date — The Standard Method
This is the most common method used by healthcare providers worldwide. It calculates your due date from the first day of your last menstrual period (LMP).
- Select the “LMP Date” Tab — Click the “LMP Date” button at the top of the calculator. This tab should be selected by default.
- Enter First Day of Last Menstrual Period — In the “First Day of Last Menstrual Period” date field, select the first day of your most recent menstrual period. Use the date picker or enter the date directly. For example, if your last period started on May 26, 2026, enter 05/26/2026.
- Enter Average Cycle Length — In the “Average Cycle Length (days)” field, enter the number of days in your typical menstrual cycle. The default is 28 days, which is the most common cycle length. If your cycles are longer or shorter, adjust this number. For example, enter 30 if your cycles typically last 30 days.
- Click “Calculate Due Date” — Press the gold “Calculate Due Date” button to see your results.
How the LMP Method Works
The calculator adds 280 days (40 weeks) to your LMP date, then adjusts for your cycle length. For a standard 28‑day cycle, the due date is exactly 280 days from LMP. For longer cycles, the due date is shifted forward by the number of extra days beyond 28. For shorter cycles, it shifts backward.
Example: LMP = May 26, 2026 + 280 days = March 2, 2027
Tab 2: Conception Date — When You Know Conception
Conception Date Tab
Use this method if you know the approximate date of conception — for example, from ovulation tracking, fertility apps, or a known date of intercourse during your fertile window.
- Click the “Conception Date” Tab — Select the middle tab at the top.
- Enter Estimated Conception Date — In the “Estimated Conception Date” field, select the date you believe conception occurred. For example, enter 07/09/2026 if you estimate conception on July 9, 2026.
- Click “Calculate Due Date” — The calculator adds 266 days (38 weeks) to your conception date to estimate the due date.
The conception date method does not require cycle length adjustment because conception marks the actual starting point of pregnancy from a biological perspective.
Tab 3: IVF Transfer — For Assisted Reproduction
IVF Transfer Tab
Use this method if you conceived through in‑vitro fertilization (IVF). The calculator adjusts based on your embryo transfer date and the age of the embryo at transfer.
- Click the “IVF Transfer” Tab — Select the rightmost tab at the top.
- Enter Embryo Transfer Date — In the “Embryo Transfer Date” field, select the date your embryo was transferred. For example, enter 07/02/2026.
- Select Embryo Age at Transfer — Use the dropdown to choose the age of your embryo at the time of transfer. Options include: Day 3 (Cleavage stage), Day 5 (Blastocyst), or Day 6 (Blastocyst). This information is available from your IVF clinic’s transfer documentation.
- Click “Calculate Due Date” — The calculator adds the appropriate number of days based on embryo age.
Day 5 Transfer: Due Date = Transfer Date + 261 days
Day 6 Transfer: Due Date = Transfer Date + 260 days
The IVF method is the most precise because the embryo age is exactly known — there is no estimation involved in the timing.
Understanding Your Results
After clicking “Calculate Due Date,” the tool displays a comprehensive pregnancy overview. Here is what each section means:
Estimated Due Date
The large highlighted result shows your estimated due date (EDD) as a full date including the day of the week. For example: “Tuesday, March 2, 2027.” This is the date your pregnancy reaches 40 weeks (280 days) from the LMP or the equivalent from your chosen calculation method.
Current Status Cards
Current Week
Week 6 + 0d
Trimester
1st
Days Remaining
238
| Card | What It Shows | How It’s Calculated |
|---|---|---|
| Current Week | Exact gestational age in weeks and days | Days since LMP ÷ 7, showing weeks + remaining days |
| Trimester | Which trimester you are currently in | Based on current gestational week |
| Days Remaining | Days until your estimated due date | EDD − Today’s date |
Progress Bar
A horizontal progress bar shows your position from Week 1 to Week 40, with markers for Trimester 2 and Trimester 3 boundaries. The yellow segment indicates how far along you are in the pregnancy.
Trimester Chart
A bar chart displays your total weeks (grey bars) and weeks completed (yellow segments) across all three trimesters, giving you a visual overview of your progress through each stage.
Pregnancy Milestones
The calculator displays key dates based on your due date:
How Each Calculation Method Works
The pregnancy due date calculator uses three medically recognized formulas. Here is the science behind each one:
Method 1: Naegele’s Rule (LMP)
Developed by German obstetrician Franz Naegele in the early 19th century, this is the most widely used method worldwide. The standard formula subtracts 3 months and adds 7 days to the LMP, or equivalently adds 280 days (40 weeks).
Adjusted: Due Date = LMP + 280 days + (Cycle Length − 28) days
Examples by cycle length:
26‑day cycle → Due date is 2 days earlier than standard
28‑day cycle → Due date is exactly 280 days from LMP
30‑day cycle → Due date is 2 days later than standard
35‑day cycle → Due date is 7 days later than standard
Why cycle length matters: The standard 280‑day calculation assumes ovulation on day 14 of a 28‑day cycle. If your cycle is longer, ovulation likely occurs later, meaning the actual gestational age is younger than what LMP alone suggests. The calculator adjusts for this automatically.
Method 2: Conception Date
This method calculates from the actual date of conception (fertilization) rather than the LMP. Since fertilization typically occurs about 14 days after LMP in a standard cycle, the timeframe is shorter.
When to use: This method is accurate when you know your conception date through ovulation tracking, fertility monitors, or documented intercourse during your fertile window.
Method 3: IVF Transfer Date
For pregnancies conceived through IVF, the embryo transfer date and embryo age are precisely known, making this the most accurate method.
Day 5 (Blastocyst): Due Date = Transfer Date + 261 days
Day 6 (Blastocyst): Due Date = Transfer Date + 260 days
Why different days? A Day 3 embryo is transferred at an earlier developmental stage than a Day 5 blastocyst. The calculator adds fewer days for older embryos because they are closer to implantation age at the time of transfer.
Trimester Breakdown
A full‑term pregnancy lasts approximately 40 weeks (280 days) from the last menstrual period, divided into three trimesters:
First Trimester
Weeks 1–13
Second Trimester
Weeks 14–27
Third Trimester
Weeks 28–40
| Trimester | Weeks | Duration | Key Developments |
|---|---|---|---|
| First | 1–13 | ~13 weeks | Organ formation, heartbeat detectable, morning sickness, early ultrasounds |
| Second | 14–27 | ~14 weeks | Anatomy scan (18–22 weeks), movement felt, gender can be determined |
| Third | 28–40 | ~13 weeks | Rapid growth, viability milestone at 24 weeks, full term at 37 weeks |
Key Pregnancy Milestones
The pregnancy due date calculator displays these important milestones based on your calculated due date:
| Milestone | Gestational Week | What Happens |
|---|---|---|
| End of First Trimester | Week 12–13 | Risk of miscarriage drops significantly; many couples share news publicly |
| Anatomy Scan | Week 18–22 | Detailed ultrasound checking baby’s organs, growth, and sometimes gender |
| Viability Milestone | Week 24 | Baby reaches a threshold where survival outside the womb becomes possible with medical care |
| Start of Third Trimester | Week 28 | Final stretch begins; baby gains weight rapidly; more frequent prenatal visits |
| Full Term Begins | Week 37 | Baby is considered full term; birth at this stage is not considered premature |
| Estimated Due Date | Week 40 | The calculated date; only about 5% of babies arrive on their exact due date |
Early Pregnancy Ultrasound vs. Due Date
If you have an early ultrasound (typically between weeks 6–12), your healthcare provider may adjust your due date based on the baby’s measurements:
| Ultrasound Timing | Accuracy | How Due Date May Change |
|---|---|---|
| 6–9 weeks | Most accurate (±3–5 days) | Likely to be used to confirm or adjust due date |
| 10–13 weeks | Very accurate (±5–7 days) | May be used to confirm or slightly adjust due date |
| 14–20 weeks | Moderate (±7–14 days) | Usually not used to change due date |
| After 20 weeks | Less accurate for dating | Due date rarely changed after first trimester |
IVF Due Date Calculation — Detailed Guide
IVF pregnancies have precisely known conception dates, making due date calculation more accurate than LMP‑based methods:
| Embryo Age | Developmental Stage | Days Added to Transfer | Equivalence |
|---|---|---|---|
| Day 3 | Cleavage stage (6–8 cells) | 263 days | Transfer date + 263 = EDD |
| Day 5 | Blastocyst (hatching) | 261 days | Transfer date + 261 = EDD |
| Day 6 | Expanded blastocyst | 260 days | Transfer date + 260 = EDD |
Why IVF due dates are more reliable: In natural conception, ovulation day must be estimated (usually day 14 of the cycle). In IVF, the embryo’s exact developmental stage and transfer date are precisely documented. This eliminates the guessing involved in LMP‑based calculations.
What If I Don’t Know My LMP or Conception Date?
- Use the earliest ultrasound date — Your healthcare provider can estimate gestational age from crown‑rump length (CRL) measurements taken during an early ultrasound.
- Estimate from ovulation signs — If you track basal body temperature, cervical mucus, or use ovulation predictor kits, you may estimate your ovulation date and work backward.
- Use the LMP tab with best estimate — Even an approximate LMP date gives a reasonable estimate within 1–2 weeks.
- Consult your healthcare provider — Your doctor or midwife will use a combination of LMP, ultrasound measurements, and physical examination to determine the most accurate due date.
Pregnancy Due Date Calculator vs. Other Health Tools
| Tool | Best For | Key Feature |
|---|---|---|
| Pregnancy Due Date Calculator | Estimating due date and pregnancy timeline | Three methods: LMP, Conception, IVF |
| Ideal Weight Calculator | Healthy weight estimation | Six medical formulas |
| BMI Calculator | Weight‑to‑height ratio | Quick health screening |
| Lean Body Mass Calculator | Body composition | Boer formula estimation |
| Body Fat Calculator | Body fat percentage | Multiple methods |
| Calorie Calculator | Daily calorie needs | Includes pregnancy adjustments |
| Protein Calculator | Daily protein targets | Goal‑based recommendations |
| Water Intake Calculator | Hydration needs | Daily water consumption |
Frequently Asked Questions
What is a pregnancy due date calculator?
A pregnancy due date calculator is a free online tool that estimates your baby’s due date using three clinically validated methods — LMP date, conception date, or IVF transfer date. It shows your estimated due date, current gestational week, trimester, days remaining, and key pregnancy milestones.
How accurate is the due date calculation?
The LMP method is accurate to within 1–2 weeks for women with regular cycles. The IVF method is the most precise because the embryo age and transfer date are exactly known. Only about 5% of babies arrive on their exact due date — most arrive within 2 weeks before or after.
Which method should I use — LMP or conception date?
Use the LMP method if you know the first day of your last menstrual period, which is the standard method used by healthcare providers. Use the conception date method if you know the approximate date of conception through ovulation tracking. Use the IVF method if you conceived through in‑vitro fertilization.
What does “Week 6 + 0d” mean?
It means you are 6 weeks and 0 days into your pregnancy from your LMP. The first number is complete weeks, and the second number is additional days. So “Week 6 + 3d” would mean 6 weeks and 3 days — or 45 total days of pregnancy.
Does cycle length affect the due date?
Yes. The standard 280‑day calculation assumes a 28‑day cycle. If your cycle is longer, ovulation occurs later and your due date shifts forward. If shorter, it shifts backward. The calculator automatically adjusts for your specific cycle length.
What embryo age should I select for IVF?
Your IVF clinic will document the embryo age at transfer — either Day 3 (cleavage stage), Day 5 (blastocyst), or Day 6 (expanded blastocyst). Check your transfer paperwork or ask your clinic. Day 5 is the most common transfer day.
Can the due date change after an early ultrasound?
Yes. If an early ultrasound (6–13 weeks) shows a significant difference between the LMP‑based due date and the baby’s measured size, your healthcare provider may adjust the due date. Ultrasounds taken before 13 weeks are the most accurate for dating.
When is a baby considered full term?
A baby is considered full term at 37 weeks of gestation. Early term is 37–38 weeks, full term is 39–40 weeks, late term is 41 weeks, and post‑term is 42 weeks and beyond.
Does the calculator save my data?
No. All calculations happen locally in your browser. Your dates, cycle length, embryo age, and results are never stored, transmitted, or shared. Your personal health information remains completely private.
External Resources — Learn More About Pregnancy Dating
- How Your Due Date Is Determined – ACOG — American College of Obstetricians and Gynecologists guide to due date calculation methods.
- Due Dates and Pregnancy – NICHD — National Institute of Child Health and Human Development information on pregnancy dating.
- Due Date Calculator – NHS UK — National Health Service guide to calculating your due date and understanding gestational age.
- Prenatal Care – Mayo Clinic — Comprehensive guide to prenatal appointments, ultrasounds, and pregnancy milestones.
- How Due Date Is Calculated – BabyCentre — Detailed explanation of due date calculation methods including IVF.
- Pregnancy Statistics – March of Dimes — Statistics on gestational age at birth, preterm delivery rates, and birth outcomes.