Due Date Calculator

Due date calculator 2026 online. Calculate baby's expected birth date and gestational age

This online tool allows you to estimate your due date (EDD), current gestational age and trimester milestones. The calculations are based on Naegele's rule, i.e. adding 280 days to the date of the first day of the last menstrual period with the correction of the cycle length. Thanks to this, future parents can easily check the approximate date of birth of the child and the progress of pregnancy.

What the calculator calculates

• Estimated due date (EDD).
• Current gestational age expressed in weeks and days.
• The trimester in which the pregnancy is.
• The most important milestones: end of the first and second trimester, due date.

How to use

1. Enter the dateof the first day of your last period.
2. Enter the averagelength of your cycle(21-45 days). By default, the calculator assumes 28 days.
3. ClickCalculateto get the results.
4. Read EDD, gestational age and approximate milestones.

How the calculator works

Calculations are based on the classic Naegele rule:

• EDD= Date of last menstrual period + 280 days + (cycle – 28).
• Gestation age= number of days from the date of menstruation → in weeks and days.
• Trimesters: I (0–13+6), II (14–27+6), III (28–40+0).
• Milestones: end of 1st trimester, end of 2nd trimester, due date.

Examples

LMP: January 1, 2025, cycle 28 days

EDD = October 8, 2025. Gestation age 12 weeks and 3 days (March). End of the first trimester: April 8, 2025, second trimester: July 15, 2025, due date: October 8, 2025.

LMP: May 15, 2025, cycle 30 days

Correction +2 days. EDD = February 21, 2026. Milestones: I trimester August 21, 2025, II trimester November 28, 2025.

LMP: September 20, 2025, cycle 26 days

Correction -2 days. EDD = June 15, 2026. Current gestational age from September 20.

Indicative table

How to calculate the due date? Naegele's rule step by step

The question "how to calculate the due date" has a classic answer from two centuries ago - the Naegele's rule, which is also used by doctors (before they specify the date for ultrasound): add 7 days to the first day of the last menstrual period, subtract 3 months and add a year.

The rule assumes a 28-day cycle - for a longer cycle, add the difference (e.g. a cycle of 32 days → +4 days), for a shorter cycle, subtract. Our calculator makes this correction automatically. Remember that only about 4-5% of babies are born exactly on their due date; Birth between the 37th and 42nd week is considered normal.

Calculate week of pregnancy - how many weeks am I?

Do you want tocalculate the week of pregnancy? Count from the first day of the last menstrual period (so-called gestational age): if, for example, 70 days have passed, you are in the 10th week of pregnancy (70 ÷ 7 = 10 full weeks, i.e. it is the 11th week - hence the frequent discrepancies "which week and what day"). The calculator above will provide the exact week and day of pregnancy and the approximate date of the next screening tests (ultrasound 11-14, 18-22 and 28-32 weeks).

FAQ

Is the result accurate?

It's just respect. The actual delivery may occur 2 weeks before or after the scheduled date.

Does the calculator take into account ultrasound examinations?

No, it is based on LMP and cycle. Ultrasound dates can vary by several days and are often more precise.

Why is cycle length important?

Naegele's rule assumes a cycle of 28 days. Longer or shorter cycles postpone the due date.

Practical tips

• Use the date of the first day of your period, not ovulation.
• Compare the result with the doctor's calculation based on the ultrasound.
• Remember that birth before the 37th week is a premature birth, after the 42nd week - after the due date.

Most common errors

• Entering the date of ovulation instead of menstruation.
• Assuming EDD = actual due date.
• Irregular cycles not taken into account.

Safety and responsible use

Calculate your due date now

You can analyze the dynamics of early pregnancy results in thebeta-hCG calculator.