Is the due date accurate?

The due date is an estimate. Most babies are born between 37 and 42 weeks, not exactly on the predicted date.

No information is stored. All calculations are done instantly on your device.

Pregnancy Due Date Calculator

Q: How is the due date calculated?

The due date is calculated using your LMP plus 280 days, adjusted for your typical cycle length. Longer cycles push ovulation later, and shorter cycles move it earlier.

Q: Why does cycle length matter?

Cycle length affects ovulation timing. If your cycle is not 28 days, your due date should be shifted forward or backward accordingly.

Calculate your estimated due date using the LMP method, adjusted for your typical cycle length.

First day of Last Menstrual Period (LMP)

Typical Cycle Length (20–45 days)

Pregnancy Due Date Calculator – Estimate Your Baby’s Arrival with Cycle Accuracy

This Pregnancy Due Date Calculator helps estimate when your baby may arrive using the first day of your Last Menstrual Period (LMP), while also adjusting the calculation based on your typical menstrual cycle length. Unlike basic calculators that assume a fixed 28-day cycle, this tool provides a more personalized and realistic due date estimate.

Global maternal-health guidance aligned with the World Health Organization (WHO) emphasizes accurate pregnancy dating for timely antenatal care, screening, and delivery planning. While ultrasound remains the clinical gold standard, LMP-based calculators remain widely used for early pregnancy tracking.

What Is a Pregnancy Due Date?

A pregnancy due date, also called the Estimated Date of Delivery (EDD), is the approximate date when a baby is expected to be born. It is traditionally calculated as 40 weeks (280 days) from the first day of the last menstrual period, not from the date of conception.

Because ovulation does not occur on the same day for every woman, especially when cycle length differs from 28 days, due dates should ideally be adjusted for individual menstrual patterns. This calculator does exactly that.

How This Pregnancy Due Date Calculator Works

The calculator uses a clinically accepted formula:

Due Date = LMP + 280 days + (Cycle Length − 28 days)

If your menstrual cycle is longer than 28 days, ovulation likely happens later, so the due date is pushed forward. If your cycle is shorter, ovulation occurs earlier, and the due date shifts earlier. This adjustment improves accuracy compared to one-size-fits-all estimates.

Understanding Gestational Age and Pregnancy Progress

Gestational age refers to how far along the pregnancy is, measured in weeks and days from the LMP. Doctors and midwives use gestational age to schedule scans, blood tests, vaccinations, and prenatal visits.

This calculator shows:

Current pregnancy duration (weeks and days)
Which trimester you are in
Approximate time remaining until delivery

Pregnancy Trimesters Explained

Pregnancy is divided into three trimesters, each with unique developmental milestones and maternal changes.

First Trimester (Weeks 1–13): Early organ development, nausea, fatigue, and important screening tests.
Second Trimester (Weeks 14–27): Rapid fetal growth, improved energy, anatomy scan, and visible baby movements.
Third Trimester (Weeks 28–40+): Final growth, weight gain, birth preparation, and delivery planning.

Pregnancy Due Date Example

Example: LMP on January 1 of 2025 with a 32-day menstrual cycle.

Base Due Date = January 1 + 280 days, Cycle Adjustment = + (32 − 28) = +4 days, Adjusted Due Date ≈ October 12 of 2025

This example shows how cycle length can meaningfully shift the estimated due date compared to a standard calculation.

Who Should Use This Pregnancy Calculator?

This tool is designed for informational and planning purposes and is useful for:

Women in early pregnancy tracking gestational age
People with cycles shorter or longer than 28 days
Couples planning prenatal appointments and milestones
First-time parents seeking clarity and reassurance
Anyone needing a quick, private pregnancy estimate

Limitations of Pregnancy Due Date Calculators

Pregnancy calculators provide estimates, not exact predictions. Only a small percentage of babies are born on their exact due date.

Accuracy may be reduced if:

Cycles are highly irregular or unknown
LMP date is uncertain or estimated
Ovulation varies significantly from cycle to cycle
Medical conditions affect cycle timing

Ultrasound dating in the first trimester is considered the most accurate clinical method for confirming gestational age.

Best Practices When Using a Due Date Calculator

Use this calculator as an early planning tool. Always confirm pregnancy dating with a qualified healthcare professional and attend recommended prenatal visits. Track trends over time rather than focusing on a single date.

Frequently Asked Questions

How is the due date calculated?

The clinical formula is: Due Date = LMP + 280 days, adjusted by your cycle length. Longer cycles shift ovulation later, and shorter cycles shift it earlier.

Why does cycle length matter?

Women with 32–35 day cycles ovulate later, so due dates are typically later. Women with 21–26 day cycles ovulate earlier, so due dates shift earlier.

Is the due date always accurate?

No. Only 4–5% of babies are born on their exact due date. Most arrive between 37 and 42 weeks.

Is my data stored?

No. All calculations occur instantly in your browser.