Free Pregnancy Due Date Calculator

Pregnancy Due Date Calculator by Conception

Get an instant, accurate estimate of your pregnancy due date. Our calculator supports LMP, conception date, and IVF transfer methods — so you know exactly when to expect your little one.

LMP MethodConception MethodIVF Method100% Free & Private

Calculate Your Due Date

Choose your preferred calculation method below

First Day of Last Menstrual Period

Accurate Results

Our pregnancy due date calculator uses the same obstetric formulas your doctor uses — Naegele's rule for LMP, 266-day rule for conception, and precise IVF transfer calculations.

Free & Private

No sign-up required. Your data never leaves your browser. We don't store or share any of your personal health information. Calculate with complete confidence and privacy.

Multiple Methods

Choose from three calculation methods — last menstrual period, conception date, or IVF transfer date. Each method is optimized for your unique pregnancy situation.

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Understanding Pregnancy Due Date Calculation by Conception Date

Calculating your pregnancy due date by conception date is one of the most accurate methods available. When you know the exact date you conceived, you can determine your estimated due date with remarkable precision. This method adds 266 days (38 weeks) to your conception date to estimate when your baby will arrive.

Key Insight

The conception method is more accurate than LMP because it does not assume a standard 28-day cycle. If you tracked ovulation or used fertility treatments, this method eliminates the guesswork about when fertilization occurred.

Many women prefer the pregnancy due date calculator by conception because it accounts for their actual cycle length. Whether your cycle is shorter or longer than the average 28 days, the conception date method provides a personalized and reliable estimate.

Adds 266 days to your known conception date for the most precise estimate
Ideal for women who tracked ovulation or used fertility monitoring
Does not rely on assumptions about your menstrual cycle length

How Our Pregnancy Due Date Calculator Works

Select Your Method

Choose from LMP, conception date, or IVF transfer. Each method is tailored to your specific situation and knowledge of your pregnancy timeline.

Enter Your Date

Input the date you know — your last period start, conception date, or IVF transfer date. Our calculator handles the rest automatically.

Get Your Results

Instantly see your estimated due date, current week of pregnancy, trimester, and weeks remaining — all in one beautiful, easy-to-read display.

Track Your Progress

Use the visual progress bar to see how far along you are in your pregnancy journey. Return anytime to check your status as weeks progress.

Calculating Due Date from Last Menstrual Period (LMP)

The LMP method is the most common way healthcare providers calculate a pregnancy due date. It uses Naegele's rule, which adds 280 days (40 weeks) to the first day of your last menstrual period. This method assumes a regular 28-day cycle with ovulation on day 14.

Important Note

If your menstrual cycles are longer or shorter than 28 days, the LMP-based estimate may be slightly off. Your healthcare provider can adjust the date based on early ultrasound measurements for greater accuracy.

The LMP calculator remains the standard in obstetric care because it provides a consistent starting point. Your doctor will refine this estimate with ultrasound dating, especially during the first trimester when measurements are most reliable.

Uses Naegele's rule: LMP date + 280 days = estimated due date
Most widely used method by healthcare providers worldwide
Best for women with regular 28-day menstrual cycles

Due Date Calculation from Conception Date

If you know your exact conception date, calculating your due date is straightforward. This method adds 266 days (38 weeks) to your conception date. It is more accurate than the LMP method because it uses the actual fertilization date rather than an assumed ovulation day.

How It Works

Conception typically occurs about 14 days after your period starts. By adding 266 days to this known date, you get a due date that accounts for your actual cycle.

Why It's Accurate

Unlike the LMP method, the conception date method does not make assumptions about your cycle length, making it ideal for irregular cycles.

Pro Tip

Tracking ovulation with basal body temperature, ovulation predictor kits, or fertility apps can help you pinpoint your conception date more accurately for a more reliable due date estimate.

IVF Transfer Due Date Calculation

For IVF pregnancies, the due date is calculated based on the embryo transfer date and the type of transfer. This method is highly accurate because the exact age of the embryo at transfer is known, eliminating the guesswork involved in other methods.

Day-3 Transfer

Adds 263 days to the transfer date. Used when a 3-day-old embryo is transferred during IVF treatment.

Day-5 Transfer

Adds 261 days to the transfer date. Used when a 5-day blastocyst is transferred during IVF treatment.

Remember

IVF dating is often considered the most precise of all methods since there is no guesswork about when fertilization occurred. Your clinic will confirm the exact embryo age at transfer.

Understanding Naegele's Rule for Due Date Estimation

Naegele's rule is the standard obstetric formula for estimating a due date. Named after German obstetrician Franz Naegele, it has been used by healthcare providers for over 150 years. The rule adds 7 days to the first day of your LMP, subtracts 3 months, and adds 1 year.

Example

If your LMP was January 1: add 7 days (January 8), subtract 3 months (October 8), add 1 year. This is equivalent to adding 280 days or 40 weeks to the LMP date.

Naegele's rule assumes a 28-day menstrual cycle with ovulation on day 14. For women with shorter or longer cycles, adjustments may be needed. Your healthcare provider may modify the estimate based on early ultrasound findings for improved accuracy.

Formula: LMP + 7 days − 3 months + 1 year = estimated due date
Assumes a 28-day cycle with ovulation on day 14
Most widely taught and used formula in obstetric practice

Pregnancy Trimesters and Your Due Date Timeline

Pregnancy is divided into three trimesters, each bringing unique changes for both you and your developing baby. Understanding what to expect in each trimester helps you navigate your pregnancy journey with confidence.

1st

First Trimester (Weeks 1-13)

The most critical period of development. All major organs begin to form. You may experience morning sickness, fatigue, and breast tenderness. Start prenatal vitamins with folic acid right away.

2nd

Second Trimester (Weeks 14-27)

Often called the “honeymoon period.” You'll feel your baby move between weeks 16-25. Your belly grows noticeably. This is a great time to prepare for your baby and enjoy the experience.

3rd

Third Trimester (Weeks 28-40+)

The home stretch! Rapid baby growth and increasing physical discomfort. Watch for signs of labor. Your healthcare visits become more frequent as you approach your due date.

Why Due Date Calculations May Vary

A due date is an estimate, not a deadline. The 40-week timeline is an average, and normal pregnancies can vary from 37 to 42 weeks. Several factors can cause your actual delivery date to differ from the calculated estimate.

First-time mothers often deliver slightly later than their due date

Irregular menstrual cycles can affect the accuracy of LMP-based calculations

Babies grow at different rates, which can affect ultrasound dating accuracy

Genetic factors and maternal health can influence when labor begins naturally

Good to Know

Only about 5% of babies are born exactly on their due date. Most arrive within a two-week window before or after. This is completely normal and expected.

Pregnancy Milestones and Week-by-Week Progress

Your pregnancy journey is marked by exciting milestones. Here are the key moments to look forward to as you progress week by week toward your due date. Each milestone represents an important step in your baby's development.

Week 6

Heartbeat Detected

Week 12

First Trimester Screening

Week 16

Feel Baby Move

Week 20

Anatomy Scan Ultrasound

Week 24

Viability Milestone

Week 28

Third Trimester Begins

Week 36

Baby is Nearly Full Size

Week 40

Due Date!

Tracking these milestones helps you understand what's happening at each stage. Use our pregnancy week calculator for a more detailed week-by-week breakdown of your unique pregnancy timeline and what to expect.