EDD Calculator (Estimated Date of Delivery)

Calculate your Estimated Date of Delivery (EDD) using either your Last Menstrual Period (LMP) or an ultrasound measurement. Enter your LMP date or your ultrasound date along with the gestational age at the time of the scan, and get your estimated due date, current gestational age, and trimester at a glance.

Disclaimer: This tool is for informational and educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before making any health-related decisions.

Calculation Method *

Enter the first day of your last menstrual period.

days

Default is 28 days. Adjust if your cycle is longer or shorter.

Enter the date when the ultrasound was performed.

weeks

Weeks of gestational age reported in the ultrasound.

days

Additional days of gestational age beyond the full weeks.

Results

Estimated Due Date (EDD)

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Current Gestational Age

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Current Trimester

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Days Until Due Date

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Estimated Conception Date

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Results Table

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Frequently Asked Questions

What is an Estimated Date of Delivery (EDD)?

The Estimated Date of Delivery (EDD), also called the due date, is the predicted date when a pregnancy is expected to reach 40 weeks of gestation. It is an estimate — only about 5% of babies are born exactly on their due date. Most births occur within two weeks before or after the EDD.

How is EDD calculated from the Last Menstrual Period (LMP)?

The most common method uses Naegele's Rule: add 280 days (40 weeks) to the first day of your last menstrual period. If your cycle length differs from 28 days, the calculation adjusts accordingly — adding extra days for longer cycles or subtracting days for shorter ones.

How is EDD calculated from an ultrasound?

When an ultrasound is performed, the sonographer measures fetal size and assigns a gestational age in weeks and days. The EDD is then calculated by subtracting the gestational age at the scan from 280 days and adding the result to the date of the ultrasound.

Which method is more accurate — LMP or ultrasound?

Ultrasound is generally more accurate, especially when performed in the first trimester (before 14 weeks). Early ultrasound can correct for irregular cycles or uncertain LMP dates. After 20 weeks, ultrasound dating becomes less precise.

What are the three trimesters of pregnancy?

The first trimester spans weeks 1–12, the second trimester covers weeks 13–26, and the third trimester runs from week 27 to delivery (around week 40). Each trimester is associated with distinct developmental milestones for the baby.

Can my due date change during pregnancy?

Yes. Your healthcare provider may adjust your EDD based on early ultrasound measurements, especially if the ultrasound date differs from the LMP-based date by more than a certain number of days. The first-trimester ultrasound is considered the gold standard for dating.

What if I have irregular periods?

If your menstrual cycles are irregular or your cycle length is not close to 28 days, the LMP-based EDD may be less reliable. In these cases, an early ultrasound is especially important for establishing an accurate due date.

What does gestational age mean?

Gestational age counts from the first day of the last menstrual period, not from conception. This means at the time of conception (around day 14 of a 28-day cycle), a pregnancy is already considered 2 weeks gestational age. A full-term pregnancy is 40 weeks gestational age.