How do I calculate my pregnancy due date from last period?

Enter the first day of your last menstrual period (LMP) and your average cycle length. The calculator adds 280 days (40 weeks) to your LMP and adjusts for cycle length. This is called Naegele's Rule and is the standard method used by doctors.

How many weeks pregnant am I today?

Enter your LMP or due date and the calculator instantly shows how many weeks and days pregnant you are. Pregnancy is counted from the first day of your last period, not from conception, so you're technically 'pregnant' for about 2 weeks before conception.

How do I calculate due date from conception date?

If you know your conception or ovulation date, add 266 days (38 weeks) to get your due date. This is more accurate than LMP calculation if you know exactly when you conceived. Enter your conception date in the calculator and select 'Conception Date' mode.

How accurate is the pregnancy due date calculator?

Due date calculations are estimates — only about 5% of babies arrive on their exact due date. Most babies are born within 2 weeks before or after. Early ultrasound dating (before 12 weeks) is most accurate, with a margin of error of about 5-7 days.

How do I calculate pregnancy with irregular periods?

For irregular periods, use your best estimate of LMP or calculate from a known ovulation/conception date. An early ultrasound is recommended to confirm dating. You can also enter your average cycle length if it differs from 28 days.

How do I calculate IVF pregnancy due date?

For IVF pregnancies, calculate from embryo transfer date. Add 266 days minus embryo age (261 days for 5-day blastocyst, 263 days for 3-day embryo). Select 'IVF Transfer' mode and enter your transfer date and embryo age.

What trimester am I in?

First trimester: weeks 1-12 (months 1-3), Second trimester: weeks 13-26 (months 4-6), Third trimester: weeks 27-40 (months 7-9). The calculator automatically shows your current trimester and progress.

How do I calculate conception date from my due date?

Subtract 266 days (38 weeks) from your due date to estimate conception. This gives you the approximate date of ovulation/fertilization. Remember that sperm can survive up to 5 days, so conception could have occurred within a window.

What is the difference between gestational age and fetal age?

Gestational age is counted from LMP (used by doctors, what this calculator shows). Fetal age is from conception, which is about 2 weeks less. At 10 weeks gestational age, the actual fetus is about 8 weeks old.

How do I use ultrasound to calculate due date?

If you have a due date from ultrasound, select 'Due Date' mode and enter that date. The calculator will work backwards to show your current weeks pregnant, conception date, and pregnancy timeline.

Pregnancy Calculator

Our free pregnancy calculator helps you determine your estimated due date (EDD), calculate exactly how far along you are in weeks and days, identify your current trimester, and track important pregnancy milestones. Calculate from your last menstrual period (LMP), conception date, IVF transfer date, or ultrasound due date.

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calendar_today Updated: April 2025

auto_awesome AI Insights AI

Hot

Calculate From

First Day of Last Period

Cycle Length 28 days

21 days 45 days

Pregnancy Progress 35%

1st Tri 2nd Tri 3rd Tri Birth

Baby Size This Week

🍋

Size of a lemon

About 8.5 cm (3.4 in)

child_care Estimated Due Date

October 8, 2026

186 days to go

Currently

14 weeks

+ 2 days

Trimester

2nd

Weeks 13-26

Key Dates

Conception Date ~Jan 15, 2026

End of 1st Trimester Mar 25, 2026

End of 2nd Trimester Jul 1, 2026

Full Term (39 weeks) Oct 1, 2026

tips_and_updates

Did You Know?

Only about 5% of babies are born on their exact due date. Most arrive within 2 weeks before or after.

Input Values

Calculate From

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auto_awesome AI Analysis

Pregnancy Timeline (LMP: Jan 1, 2026):

Due date: October 8, 2026
Current: 13 weeks, 4 days (2nd trimester)
Conception: ~January 15, 2026
Baby size: About the size of a lemon

Only 5% of babies arrive on their due date. Most arrive within 2 weeks before or after.

lightbulb Tips

•Only 5% of babies arrive on due date
•Full term is 39-40 weeks pregnant
•Early ultrasound is most accurate
•Pregnancy counted from last period

child_care Trimesters

1st Trimester Weeks 1-12

2nd Trimester Weeks 13-26

3rd Trimester Weeks 27-40

Key Milestones

Early Term 37-38 weeks

Full Term 39-40 weeks

How to Use This Calculator

calculate

Select Calculation Method

Choose to calculate from LMP, conception date, IVF transfer, or known due date.

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Enter Your Date

Enter the relevant date based on your selected method.

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Adjust Cycle Length

If your cycle differs from 28 days, enter your average cycle length.

child_care

View Results

See your due date, current week, trimester, and pregnancy timeline.

The Formula

Naegele's Rule calculates due date by adding 280 days (40 weeks) to the first day of your last menstrual period. For conception date, add 266 days (38 weeks). Cycle length adjustments are made for cycles shorter or longer than 28 days.

Due Date = LMP + 280 days

lightbulb Variables Explained

Due Date Estimated delivery date (EDD)
LMP First day of last menstrual period
280 days 40 weeks (average pregnancy duration)

tips_and_updates Pro Tips

The most accurate due date comes from an early ultrasound (before 12 weeks)

Only 5% of babies are born on their exact due date

Full-term pregnancy is between 39-40 weeks; early term is 37-38 weeks

First trimester: weeks 1-12, Second: weeks 13-26, Third: weeks 27-40

Conception typically occurs about 2 weeks after your last period

Longer menstrual cycles may shift your due date later

Pregnancy Calculator - Due Date & How Far Along

Our free pregnancy calculator helps you find your estimated due date, calculate exactly how many weeks and days pregnant you are, track your pregnancy progress through each trimester, and estimate your conception date. Works with LMP, conception date, IVF transfer, or ultrasound due date.

Due Date Calculator by Last Period

Calculate your pregnancy due date using the first day of your last menstrual period (LMP). Our calculator uses Naegele's Rule, adding 280 days (40 weeks) to your LMP. Adjust for your cycle length if it's different from the standard 28 days for more accurate results.

How Far Along Am I Calculator

Find out exactly how many weeks and days pregnant you are today. Enter your LMP or due date and instantly see your current gestational age, trimester, and pregnancy progress percentage. Track your journey week by week.

Conception Date Calculator

Estimate when conception occurred based on your due date or LMP. Conception typically happens about 14 days after the start of your last period (at ovulation). Calculate backwards from your due date to find your approximate conception window.

IVF Pregnancy Due Date Calculator

Calculate your due date for IVF pregnancies using your embryo transfer date. The calculator adjusts based on whether you had a 3-day embryo or 5-day blastocyst transfer for accurate due date estimation.

Pregnancy Trimester Calculator

Know which trimester you're in and track your progress through each stage. First trimester (weeks 1-12) covers early development, second trimester (weeks 13-26) brings visible growth, and third trimester (weeks 27-40) prepares for birth.

Frequently Asked Questions

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