How accurate is a due date calculator?

Our calculator uses the standard method of adding 280 days (40 weeks) to the first day of your last menstrual period (LMP). It's highly accurate for those with regular cycles, but remember that only about 5% of babies arrive on their exact due date. It's a trusted estimate used by doctors worldwide.

What if I don't know my LMP date?

If your LMP date is unknown, the most accurate way to determine your due date is through a dating ultrasound, which your healthcare provider can perform. If you know your conception date, you can add 266 days to get a close estimate.

Why is pregnancy calculated from the last period?

While conception typically happens about two weeks after your period starts, the first day of the LMP is a more certain and easily identifiable date. This standardized method, known as calculating gestational age, ensures consistency among all healthcare providers.

How does the trimester calculation work?

Pregnancy is divided into three trimesters: First (weeks 1-13), Second (weeks 14-27), and Third (week 28 to birth). Each has distinct developmental milestones. Our calculator automatically determines which trimester you are in.

Can this calculator be used for IVF pregnancies?

For IVF, dating is more precise. You should use your embryo transfer date, not your LMP. For a 3-day embryo transfer, add 263 days. For a 5-day embryo transfer, add 261 days. Always confirm with your fertility specialist.

Now that I have my due date, what's next?

Congratulations! Your first step should be to schedule an appointment with a healthcare provider (OB-GYN or midwife) to confirm the pregnancy and start prenatal care. They will guide you on nutrition, prenatal vitamins, and the next steps for a healthy pregnancy.

Can my due date change?

Yes, it's possible. The initial due date from your LMP is an estimate. Your doctor may adjust your due date after a first-trimester ultrasound, which measures the baby's size and can provide a more accurate age. This is especially common if your cycles are irregular.

What is an 'anatomy scan'?

The anatomy scan is a detailed ultrasound typically performed between weeks 18 and 22 of pregnancy. A sonographer will check the baby's major organs, limbs, and overall physical development. It's also when you can often find out the baby's sex if you choose to.

How is a 'pregnancy week' counted?

If you are '10 weeks and 4 days' pregnant, you are in your 11th week. Just like when a baby is 6 months old, they are in their first year of life. So, when our calculator shows you are 10 weeks pregnant, it means you have completed 10 full weeks and are now living in your 11th.

Is it normal to go past my due date?

Yes, very normal. Many first-time mothers go past their estimated due date. A pregnancy is considered 'post-term' if it extends beyond 42 weeks. Your healthcare provider will monitor you and your baby closely and may discuss inducing labor if necessary.

Due Date Calculator

Our advanced Due Date Calculator helps expectant parents determine their baby’s estimated arrival date based on the first day of the last menstrual period (LMP) or conception date. This essential tool provides key milestones throughout your pregnancy journey.

Calculation Method

Select Date

Average Cycle Length (days)

Your Pregnancy Timeline

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Estimated Due Date

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Conception Date

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Current Trimester

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Weeks Pregnant

Key Pregnancy Milestones

Understanding How Your Due Date is Calculated

While our calculator does the heavy lifting, understanding the methods behind it can be empowering. The two most common methods are:

Naegele’s Rule (LMP Method): This is the standard method used by most healthcare providers. It assumes a 28-day menstrual cycle where ovulation occurs on day 14. The rule is simple: take the first day of your last menstrual period (LMP), subtract three months, and add seven days. This gives an estimated due date of 280 days (or 40 weeks) from your LMP.

Conception Date Method: If you know the exact date of conception (common with IVF or ovulation tracking), you can calculate the due date more directly. A typical full-term pregnancy lasts about 38 weeks (266 days) from the date of conception. This method is often more accurate but relies on knowing the precise moment of fertilization.

It’s important to remember that these are estimations. An early ultrasound is the most accurate way to determine your baby’s gestational age and confirm your due date.

Why Knowing Your Due Date Matters

Accurate Planning

Prepare for your baby’s arrival by knowing when to start maternity leave and arrange support.

Prenatal Care

Schedule important prenatal tests and ultrasounds at optimal times during your pregnancy.

Baby Development

Track your baby’s growth and development week by week throughout your pregnancy journey.

Your Pregnancy Journey: A Trimester-by-Trimester Guide

First Trimester (Weeks 1-13)

This is a period of rapid development. Your baby’s major organs and body systems form. You might experience morning sickness, fatigue, and food cravings as your body adjusts to hormonal changes.

Second Trimester (Weeks 14-27)

Often called the “honeymoon” phase of pregnancy. Early symptoms usually subside, and you’ll likely feel more energetic. You’ll begin to feel your baby move, and an anatomy scan around week 20 will check their growth.

Third Trimester (Weeks 28-40+)

The final stretch! Your baby grows rapidly, gaining weight and preparing for birth. You may feel more discomfort, such as backaches and shortness of breath, as your baby takes up more space. It’s time to finalize birth plans and pack your hospital bag.

Preparing for Your Baby’s Arrival

Once you have your estimated due date, the countdown begins! Here are a few key things to consider as you prepare:

Discuss a Birth Plan: Talk to your healthcare provider about your preferences for labor and delivery.
Prepare the Nursery: Set up a safe and comfortable space for your baby to sleep.
Pack Your Hospital Bag: Have a bag ready with essentials for you, your partner, and the baby for when labor begins.
Install the Car Seat: Ensure you have an approved infant car seat properly installed in your vehicle.
Take a Class: Consider childbirth, breastfeeding, or infant care classes to build confidence.

Common Signs of Labor

As your due date approaches, be on the lookout for these signs that labor might be starting. Remember to contact your doctor or midwife if you think you are in labor.

Strong, Regular Contractions: Contractions that become progressively stronger, last longer, and occur closer together.
Water Breaking: A gush or a steady trickle of amniotic fluid from the vagina.
Losing the Mucus Plug: The release of the “bloody show,” a small amount of mucus and blood that has sealed the cervix.
Lightening: A feeling that the baby has “dropped” lower into your pelvis, which can make breathing easier.
Cervical Changes: Effacement (thinning) and dilation (opening) of the cervix, which can only be confirmed by a healthcare provider.