Quick Calculators

Pregnancy Due Date Calculator

Enter the first day of your last period (LMP) or your conception date to calculate your estimated due date (EDD) and track your trimester milestones.

Standard cycle is 28 days.

Estimated Due Date
Tuesday, May 11, 2027
You are exactly 0 weeks and 0 days pregnant.
End of First Trimester (Week 13)Tuesday, November 3, 2026
End of Second Trimester (Week 27)Tuesday, February 9, 2027
Estimated Conception DateTuesday, August 18, 2026
Medical Disclaimer: This calculator provides an estimate based on standard averages (Naegele's rule). Only a healthcare provider can accurately confirm a pregnancy and provide a definitive due date via an ultrasound.

Last updated: July 2026

Understanding Your Pregnancy Timeline

Finding out you are pregnant is one of the most exciting moments of your life. Naturally, the very first question everyone asks is: "When are you due?" Our Pregnancy Calculator uses standard medical formulas to give you an estimated due date (EDD) and break down your trimester milestones.

How Naegele's Rule Works

Obstetricians and midwives calculate due dates using Naegele's Rule. This formula assumes a standard 28-day menstrual cycle and a 280-day (40-week) gestation period.

The math is: First day of LMP + 7 days - 3 months + 1 year = EDD

Because every woman's body is different, our calculator allows you to adjust the average length of your cycle. If your cycle is 32 days long, ovulation likely happens later, meaning your due date will be pushed back by 4 days compared to a 28-day cycle.

A Worked Example

Say your last period started on January 1, and you have a typical 28-day cycle. Adding 280 days gives an estimated due date of October 8. If your cycle runs longer, say 32 days, that same January 1 start date shifts your due date about 4 days later, to around October 12 — because a longer cycle usually means ovulation and conception happened later too.

When to Use Your Conception Date

If you were tracking your ovulation perfectly (using basal body temperature or ovulation strips), or if you conceived via IUI, you may know the exact day of conception. In this case, you can bypass the LMP calculation entirely. The due date is simply Conception Date + 266 days. If you conceived via IVF and know your embryo transfer date specifically, our IVF Due Date Calculator is built around that date instead for a more precise result.

Gestational Age vs. Fetal Age

One of the most common points of confusion in early pregnancy: the "weeks pregnant" you'll hear from your doctor (gestational age) is counted from your last period, not from conception. Since conception typically happens about two weeks after your last period started, your baby's actual age is roughly two weeks younger than your pregnancy week count. This isn't a discrepancy or an error — it's just the medical standard, and it's the same convention this calculator, your doctor, and every dating ultrasound will use.

What Happens at the First Ultrasound?

While our calculator provides an estimate based on your dates, your healthcare provider will confirm this date during your first "dating ultrasound" (usually around 8 to 12 weeks). Because early fetal growth is highly predictable, the ultrasound technician will measure the crown-to-rump length (CRL) of the fetus. If the ultrasound date differs from your LMP date by more than a few days, your doctor may officially change your due date to match the ultrasound.

Frequently Asked Questions

Due dates are traditionally calculated using Naegele's rule, which adds 280 days (40 weeks) to the first day of your Last Menstrual Period (LMP). If your cycle is longer or shorter than the average 28 days, the calculation is adjusted accordingly.
No, a due date is simply an estimate. Only about 4% to 5% of babies are actually born on their exact due date. A pregnancy is considered 'full term' anywhere between 39 weeks and 40 weeks and 6 days.
Because it's very difficult to pinpoint the exact day of ovulation and conception, the medical standard is to start the clock on the first day of your last period. This means during 'Week 1' and 'Week 2' of your pregnancy, you actually weren't pregnant yet!
Gestational age is counted from the first day of your last period, which is what doctors, ultrasounds, and this calculator use. Fetal age (or conceptional age) is counted from the actual date of conception, roughly two weeks later. So at '10 weeks pregnant' (gestational age), the embryo or fetus itself is closer to 8 weeks old. Medical care always uses gestational age unless a provider specifically says otherwise.
This calculator lets you adjust your average cycle length, which helps account for cycles longer or shorter than 28 days, but a highly irregular cycle makes the LMP method less reliable. If you know your conception date (for example, from ovulation tracking or IUI/IVF), switch to that method instead. Otherwise, a first-trimester dating ultrasound is the most accurate way to confirm your due date.
You can use the 'Known Date of Conception' method if you know your egg retrieval or ovulation date. If you know your embryo transfer date instead, our dedicated IVF Due Date Calculator is built specifically around 3-day and 5-day transfer dates, which gives a more precise estimate for IVF pregnancies.
For a regular, well-tracked cycle, the LMP method is accurate to within about a week for most pregnancies. Ultrasound dating in the first trimester is generally considered the most accurate method overall, since early fetal growth is highly consistent across pregnancies. Your due date is always an estimate — treat it as a helpful planning window, not an exact prediction.