Free Pregnancy Tool · 2026

Pregnancy Due Date Calculator

Find your due date, current week, trimester, and key pregnancy milestones. Calculate from last period, conception date, or IVF transfer.

Last updated · Dating rules checked against ACOG Committee Opinions 700, 579 and 797

LMP, Conception & IVF Methods
Week-by-Week Milestones
Trimester Tracker
No Signup
Our networkfavorit5The 5 worth buying.Top fives, comparisons and what reviewers say.See the top 5s
Pregnancy Due Date Calculator
Due Date · Current Week · Milestones
Most common method: adds 280 days (40 weeks)
Estimates only. Only your healthcare provider can confirm your due date via ultrasound. Always consult your OB/GYN or midwife.
🤰

Enter your information above to find your due date and pregnancy milestones.

Our networkLegalCost.usLegal costs, calculated for your stateChild support, alimony, DUI fines and injury settlements. Free and instant.Open LegalCost.us
Our networkdiscount5Fresh deals. Five at a time.Only the offers worth a click, with the ones ending soonest on top.Price dropsCoupon codesClearance and flash salesFree shipping offersSee today’s dealsEnding soonest first.

How Your Due Date is Calculated

Your due date is 280 days (40 weeks) after the first day of your last menstrual period, assuming a 28-day cycle. A last period that started on September 1, 2026 gives a due date of June 8, 2027. The calculator above also adjusts for longer or shorter cycles and works from a known conception date or an IVF transfer date.

The most common method is Naegele's Rule: take the first day of your last menstrual period (LMP), add 280 days (40 weeks). This assumes a 28-day cycle with ovulation on day 14. If your cycle is shorter or longer, the due date is adjusted accordingly.

About 4% of babies are born exactly on their due date. Most arrive within two weeks before or after. The most accurate confirmation comes from a first-trimester ultrasound (before week 14), which can narrow the estimate to within 5 to 7 days.

The Three Trimesters

First Trimester (Weeks 1 to 13)

Major organ development. The embryo becomes a fetus at week 10. Miscarriage risk is highest in this period and drops significantly after week 12. Morning sickness typically peaks at weeks 8 to 10.

Second Trimester (Weeks 14 to 27)

Often the most comfortable period. The anatomy scan (18 to 20 weeks) checks the baby's development and can often show the sex. Baby movements become noticeable around weeks 18 to 22.

Third Trimester (Weeks 28 to 40)

Baby gains most of its weight. Lungs mature. Baby moves into position for delivery. Kick counts begin around week 28. Full term is defined as 39 to 40 completed weeks.

IVF Due Date Calculation

For IVF pregnancies, the due date is counted from the embryo transfer date and the age of the embryo. 3-day transfer: add 263 days. 5-day blastocyst: add 261 days. Both work out to 266 days from fertilization, which is known exactly, so the date is more precise than an LMP estimate.

Due Date by First Day of Last Period

Due dates below are an exact count of 280 days for a 28-day cycle. The Naegele shortcut (add 7 days, subtract 3 months, add 1 year) is quicker to do in your head, but it can land up to 3 days later because months have different lengths.

Last period startedDue date (280 days)Naegele shortcut
Jan 1, 2026Oct 8, 2026Oct 8, 2026
Feb 1, 2026Nov 8, 2026Nov 8, 2026
Mar 1, 2026Dec 6, 2026Dec 8, 2026
Apr 1, 2026Jan 6, 2027Jan 8, 2027
May 1, 2026Feb 5, 2027Feb 8, 2027
Jun 1, 2026Mar 8, 2027Mar 8, 2027
Jul 1, 2026Apr 7, 2027Apr 8, 2027
Aug 1, 2026May 8, 2027May 8, 2027
Sep 1, 2026Jun 8, 2027Jun 8, 2027
Oct 1, 2026Jul 8, 2027Jul 8, 2027
Nov 1, 2026Aug 8, 2027Aug 8, 2027
Dec 1, 2026Sep 7, 2027Sep 8, 2027

How Cycle Length Moves the Date

The 280-day rule assumes you ovulated about 14 days after your period started, which fits a 28-day cycle. The second half of the cycle (ovulation to the next period) stays close to 14 days for most people, so a longer cycle means later ovulation and a later due date. The adjustment is simple: add one day for every day your cycle is longer than 28, and subtract one for every day it is shorter.

Cycle lengthAdjustmentDue date for a Sep 1, 2026 period
21 daysminus 7 daysJun 1, 2027
24 daysminus 4 daysJun 4, 2027
28 daysnoneJun 8, 2027
30 daysplus 2 daysJun 10, 2027
32 daysplus 4 daysJun 12, 2027
35 daysplus 7 daysJun 15, 2027

If your cycles are irregular, an early ultrasound gives a more reliable date than any cycle adjustment. The due date by ultrasound calculator works from the gestational age on your scan report.

Key Weeks for a June 8, 2027 Due Date

Pregnancy weeks are counted from the first day of the last period, so at conception you are already about 2 weeks pregnant. Here is how the main dates fall for a last period on September 1, 2026, using the term definitions from the American College of Obstetricians and Gynecologists (ACOG).

WeekDateWhat it means
2 weeks 0 daysSep 15, 2026Likely conception (28-day cycle)
4 weeks 0 daysSep 29, 2026Missed period, home test usually positive
13 weeks 6 daysDec 7, 2026Last day of the first trimester
14 weeks 0 daysDec 8, 2026Second trimester starts
20 weeks 0 daysJan 19, 2027Halfway, around the anatomy scan
28 weeks 0 daysMar 16, 2027Third trimester starts
37 weeks 0 daysMay 18, 2027Early term (37 weeks to 38 weeks 6 days)
39 weeks 0 daysJun 1, 2027Full term (39 weeks to 40 weeks 6 days)
40 weeks 0 daysJun 8, 2027Estimated due date
41 weeks 0 daysJun 15, 2027Late term (41 weeks to 41 weeks 6 days)
42 weeks 0 daysJun 22, 2027Post-term

When an Ultrasound Changes the Date

ACOG advises that an ultrasound in the first trimester (up to 13 weeks 6 days) is the most accurate way to date a pregnancy. If the scan and your LMP date disagree, the ultrasound date is used when the gap is more than 5 days before 9 weeks, or more than 7 days from 9 weeks to 13 weeks 6 days. Later scans need bigger gaps before the date is changed, and once your provider has set a due date from the earliest scan it normally stays put.

For IVF, ACOG says the due date should come from the embryo's age and the transfer date: 263 days after a day-3 transfer and 261 days after a day-5 transfer. That is why the IVF options above do not ask for a period date.

Method and sources. Due date = first day of last menstrual period + 280 days, plus (cycle length minus 28) days for cycles other than 28 days. Conception method: conception date + 266 days. IVF: transfer date + 263 days (day-3 embryo) or + 261 days (day-5 embryo). All dates in the tables were computed with the same day count as the calculator. Sources: ACOG Committee Opinion 700, Methods for Estimating the Due Date; ACOG Committee Opinion 579, Definition of Term Pregnancy; ACOG Committee Opinion 797 on Group B strep screening; MedlinePlus. These are estimates; your doctor or midwife confirms the official due date.

After the birth, the baby weight percentile calculator uses the WHO growth standards that US paediatricians follow up to age two.

This calculator provides estimates only. Your healthcare provider will confirm your official due date via ultrasound measurement. Always follow your OB/GYN's guidance.
Our networkLegalCost.usWhat will your legal case cost?Official formulas for all 50 states. Free, no signup.Check your state
Track your pregnancy week by week: free app
Daily tips, baby development updates, and expert advice from OB/GYNs
Get the App →
Sponsored: we may earn a commission if you download through this link, at no cost to you.

Frequently Asked Questions

The standard method is Naegele's Rule: take the first day of your last menstrual period, add 7 days, subtract 3 months and add 1 year, which comes to about 280 days (40 weeks). Depending on the months involved the shortcut can land up to 3 days after an exact 280-day count, so this calculator counts the days exactly. This assumes a 28-day cycle with ovulation on day 14. If your cycle is shorter or longer, the calculator adjusts accordingly. About 4% of babies are born exactly on their due date. Most arrive within 2 weeks before or after.

An LMP-based due date is an estimate with a margin of roughly 2 weeks. The most accurate method is a first-trimester ultrasound (before 14 weeks), which narrows the estimate to within 5 to 7 days by measuring the embryo directly. ACOG advises switching to the ultrasound date when the two differ by more than 5 days before 9 weeks, or by more than 7 days from 9 weeks to 13 weeks 6 days. Early ultrasounds are more accurate than later ones for dating purposes.

The first trimester runs from weeks 1 to 13 (roughly 3 months). The second trimester covers weeks 14 to 27, often the most comfortable period with reduced nausea and visible baby movements. The third trimester is weeks 28 to 40, when the baby gains most of its weight and prepares for birth. Full-term is defined as 39 to 40 weeks; preterm is before 37 weeks; late preterm is 34 to 36 weeks; early term is 37 to 38 weeks.

For IVF pregnancies, the due date is calculated from the embryo transfer date and the age of the embryo, not your last period. For a 3-day embryo transfer, add 263 days to the transfer date. For a 5-day blastocyst transfer, add 261 days. This is more precise than LMP-based calculation because the exact fertilization date is known. Your fertility clinic will confirm the official due date at your first OB appointment via ultrasound.

Full-term pregnancy is defined as 39 weeks 0 days through 40 weeks 6 days. "Early term" is 37 to 38 weeks; "full term" is 39 to 40 weeks; "late term" is 41 weeks; "post-term" is 42+ weeks. Babies born at 37 to 38 weeks have slightly higher risks than those born at full term. If labor has not started, induction is usually offered between 41 and 42 weeks, because risks rise once a pregnancy passes the due date.

First trimester: blood type and Rh factor, CBC, STI screening, first-trimester genetic screening (nuchal translucency ultrasound + blood test), and cell-free DNA testing (NIPT) at 10+ weeks. Second trimester: anatomy scan at 18 to 20 weeks, quad screen, gestational diabetes screening (glucose challenge at 24 to 28 weeks). Third trimester: Group B strep test at 36 to 37 weeks, repeat blood tests, and non-stress tests if indicated. Testing varies by age and risk factors.

Yes: it is very common. If the ultrasound measurement differs from the LMP-based date by more than 5 days before 9 weeks or 7 days from 9 to 15 weeks 6 days (10 days from 16 to 21 weeks 6 days, 14 days from 22 to 27 weeks 6 days), your provider will typically update the official due date to match the ultrasound. This is more accurate and does not mean anything is wrong. Irregular cycles, uncertain LMP dates, or early conception timing all affect the LMP calculation.

Medically, pregnancy weeks are counted from the first day of your last menstrual period (LMP); this is called gestational age. Fetal age (from actual conception) is about 2 weeks less than gestational age. When your doctor says you are "12 weeks pregnant," they mean 12 weeks gestational age. The reason for this convention is that LMP is usually known even when the exact conception date is not. All pregnancy milestones use gestational age.

Yes, but irregular cycles make it harder to predict ovulation and calculate a due date from LMP. Ovulation tracking (basal body temperature charts, ovulation predictor kits or cycle-tracking apps) can help identify your fertile window. If cycles vary significantly (shorter than 21 days or longer than 35 days), consulting a gynecologist is advisable. An early ultrasound is especially important for accurate dating when periods are irregular.

Gestational age counts from the first day of your last menstrual period and is the standard medical measurement used for all prenatal care and developmental milestones. Fetal age (conceptional age) counts from actual fertilization: typically 2 weeks less than gestational age. When your provider says "week 20 anatomy scan," they mean 20 weeks gestational age, even though the embryo has only been developing for about 18 weeks. All this calculator's results use gestational age.

Start with the usual rule, first day of your last period plus 280 days, then add the number of days your cycle is longer than 28, or subtract the days it is shorter. With a last period on September 1, 2026, a 35-day cycle gives June 15, 2027 instead of June 8, and a 24-day cycle gives June 4. If your cycle length changes a lot from month to month, the adjustment is only a rough guide and an early ultrasound will usually set the date.

The same way as a fresh transfer: the date comes from the age of the embryo on the day it was transferred. Add 261 days to the transfer date for a day-5 blastocyst and 263 days for a day-3 embryo. A day-5 frozen transfer on October 1, 2026 gives a due date of June 19, 2027. Your clinic may use a slightly different convention for day-6 embryos, so check the date they give you.
More Health Calculators
BMI Calculator
Health
Calorie Calculator
Health
Ideal Weight
Health
Ovulation Calculator
Health
Period Calculator
Health
Water Intake
Health
Sleep Calculator
Health
BMR Calculator
Health
Baby Budget
Finance
Age Calculator
Time & Date