Pregnancy Due Date Calculator: Find Out How Far Along You Are

Estimate when your baby will arrive with our pregnancy due date calculator!

Updated May 17, 2023
Woman with pregnancy test

The moment you find out that you're pregnant, one of the first thoughts that comes to mind is when your little bundle of joy will arrive! A pregnancy due date calculator can help you determine an estimated date of when you'll give birth. This can also provide you with a clear idea of when to ask off from work, the best time to plan your baby shower, and how long you have to start saving before your baby's big debut. Go ahead - calculate your due date now!

LoveToKnow Pregnancy Due Date Calculator

Use the calculator below to estimate your due date and the current estimated weight and length of your baby.

Information Needed for a Due Date Calculation

Most online due date calculators only require the first day of your last period and the number of days in your normal menstrual cycle to calculate your due date. However, there are other platforms that give you the option of determining this date based on:

  • Your likely date of conception
  • Your estimated due date
  • An IVF transfer date
  • Early ultrasound

How Does the Calculator Work?

There are several methods for calculating your due date using a pregnancy calculator. The tool above uses the last menstrual period method, but there are several other ways to calculate due dates manually as well.

Common Ways to Calculate Your Due Date

Some of the typical techniques for calculating due dates include the following:

Last Menstrual Period Method

This is the most common method for determining your potential delivery date. Calculators that employ this process add 280 days to the first day of your last menstrual cycle. This is based on the belief that pregnancy lasts for 266 days: 280 days minus the estimated 14 days from the start of your menstrual cycle until ovulation.

The date of your ovulation is an estimate; many women may ovulate before or after day 14. Because of this uncertainty, the due date calculation is considered an approximation.

Naegele's Rule

Another way to calculate due dates is with the Naegele's Rule. If you know the first day of your last menstrual period, the calculation is simple. You count back 3 months from this date and add 7 days.

Many doctors use this method in their offices since they can quickly calculate due dates using a desk calendar. This method assumes that your menstrual cycle is an average of 28 days in length and that ovulation occurs on day 14.

Basal Body Temperature

Basal body temperature (BBT) is your baseline temperature, which is measured first thing in the morning before you do anything - including getting out of bed. If you measure your BBT every day, you will typically notice a temperature elevation during your ovulation window. With this information, you take the day of ovulation and add 266 days to it. This will give you your delivery date.

Some pregnancy sites have charts where you can track this data and calculate your potential due date. If you know your date of conception, for instance, if you underwent a fertility procedure, you can also add 266 days to that date as well.

Calculating Your Due Date Manually

Take the date of the first day of your last normal menstrual period and add 7 days to it. Then, add nine months to get your due date.

What If You Have an Irregular Menstrual Cycle?

Online due date calculators work best when you have a regular period. It is advisable to discuss your due date with your health care professional, in the event your cycle is irregular. Your OB-GYN will likely suggest the use of an ultrasound to clarify your conception and due dates.

Other Free Pregnancy Calculators Online

There are several other free online pregnancy calculators that you can use. Here are some examples:

  • This tool can calculate a due date based on last period, conception date, IVF transfer date, or early ultrasound scan.
  • You can calculate due date according to your last period, conception date, IVF transfer date, or early ultrasound scan. You can also use this tool if you already know your due date to get a timeline of your pregnancy.

These calculators require specific information in order to determine your potential due date. Along with the results of your online due date calculation, these websites also offer a pregnancy calendar overview, fun facts about your baby's potential birth month, links to other pregnancy related information, and resources for receiving online support during your pregnancy.

Due Dates Can Change: Remember They're Only Estimates

While due date calculators can give you a general idea of when to expect to birth your baby, there are many factors that may lead to your baby arriving before or after this day. In fact, less than ten percent of all pregnancies result in a delivery on the estimated due date, so it is just that - an estimate.

Full-term babies will be born somewhere between 37 and 40 weeks from the first date of your last period, but some mothers have to wait until 42 weeks to meet their sweet little one. Also, not all babies are born at full term. Health issues, accidents, and multiple births can all play into when your baby will actually be born. The uncertainty is par for the course, so your best plan is to get prepared for your baby's arrival early and then try to relax until the day comes!

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Pregnancy Due Date Calculator: Find Out How Far Along You Are