How is a pregnancy due date calculated?

A due date is an estimate of when your pregnancy may reach full term. It’s usually based on the first day of your last period, or on ovulation, conception, or embryo transfer if those dates are known. At Spring, we don’t rely on a single formula. Your care team looks at your full picture—including early ultrasound—to shape a timeline that reflects your pregnancy, not just a general estimate.

How accurate is a due date calculator?

A due date calculator is a helpful starting point—but it isn’t exact. Most pregnancies don’t follow a single fixed date. What matters more is understanding your range and how your pregnancy is progressing over time. That’s something your care team continues to refine with you as your pregnancy develops.

What is the most accurate way to calculate a due date?

The most accurate method depends on how your pregnancy began. Early ultrasound often gives the clearest picture for natural conception. If you were tracking ovulation, that can help refine your estimate. With IVF, timing is known—so your due date can be calculated with a high level of confidence from the start.

How do I calculate my due date from my last menstrual period (LMP)?

Most due dates are estimated by adding 40 weeks to the first day of your last period. This works best for people with regular cycles. If your cycle length varies or you’re unsure of your dates, your timeline may need a closer look. Your care team can help adjust your estimate so it better reflects your pregnancy.

Can I calculate my due date based on ovulation or conception date?

Yes. If you know when ovulation or conception occurred, you can estimate your due date from that timing. This often gives a more personalized estimate, especially if your cycles aren’t regular. At Spring, we take that information and layer in clinical insight to make sure your timeline feels clear and grounded.

How is a due date calculated after IVF?

With IVF, we know exactly when fertilization and embryo transfer happen. That means your due date isn’t based on estimates—it’s based on known timing. At Spring, we use that clarity to map your pregnancy from the very beginning, so you always have a clear understanding of where you are and what comes next.

What is my due date for a Day 5 embryo transfer?

For a Day 5 embryo transfer, your due date is calculated based on the embryo already being five days developed at the time of transfer. Because the timing is so precise, this method gives a more exact estimate than approaches based on cycle tracking alone. If you’re unsure how to calculate it, your care team can walk you through it.

Why might my due date change during pregnancy?

It’s normal for your due date to shift slightly, especially early on. As more information becomes available—like ultrasound measurements—your timeline may be adjusted to better reflect how your pregnancy is progressing. This is simply part of getting a clearer, more accurate picture over time.

Is an ultrasound more accurate than LMP for determining due date?

In many cases, yes. Early ultrasound allows your provider to measure development directly, which can be more reliable than estimating based on cycle timing alone. That’s why your timeline may evolve as more information comes in—it’s all part of making sure your care stays aligned with your pregnancy.

Do pregnancies usually reach their exact due date?

Most pregnancies don’t follow an exact schedule. It’s very common for delivery to happen within a range of time around the due date. Your due date is best thought of as a guide—something that helps shape your care, your milestones, and your expectations along the way.

Your journey
begins here.

Calculate your estimated due date and key milestone appointments based on your treatment type. Every pregnancy timeline is different. Use the calculator as a starting point—and if you want a more personalized understanding, our care team is here to help

Due Date Calculator

Select your treatment type to get started

Treatment Type

Natural Conception, Timed Intercourse, Ovulation Induction (IUI) Ovulation Induction — based on last menstrual period

Embryo Transfer — Cleavage Stage (Day 3) Fresh or frozen Day 3 embryo transfer

Embryo Transfer — Blastocyst (Day 5, 6, or 7) Fresh or frozen blastocyst transfer

First Day of Your Last Menstrual Period (LMP)

Embryo Transfer Date

Your Estimated Timeline

Estimated Due Date

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Weeks Until Due Date —

These dates are estimates based on standard obstetric calculations and are provided for informational purposes only.
Always confirm timing with your Spring Fertility care team and OB/GYN.
ACOG Guidelines: Methods for Estimating the Due Date →

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are deeply individual.

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Your journey
begins here.

Calculate your estimated due date and key milestone appointments based on your treatment type. Every pregnancy timeline is different. Use the calculator as a starting point—and if you want a more personalized understanding, our care team is here to help

Due Date Calculator

Fertility journeys
are deeply individual.

Please complete to schedule a session.

Please complete to schedule a session.

Please complete to schedule a session.

Your journey begins here.

Calculate your estimated due date and key milestone appointments based on your treatment type. Every pregnancy timeline is different. Use the calculator as a starting point—and if you want a more personalized understanding, our care team is here to help

Due Date Calculator

Fertility journeys are deeply individual.

Your journey
begins here.

Fertility journeys
are deeply individual.