How to Calculate Your Due Date
One of the most common questions from expectant parents is "how to calculate your due date?" The Lunara pregnancy due date calculator uses the first day of your last menstrual period (LMP) as the starting point. This is the standard method used by healthcare professionals and offers a straightforward way to estimate when your baby is likely to arrive.
First day of your last menstrual period
By entering the first day of your LMP into Lunara’s calculator, the tool automatically adds 280 days (or 40 weeks) to give you your estimated due date. This method assumes a typical 28-day menstrual cycle and ovulation occurring around day 14.
This is a great starting point for most people, especially if you have regular cycles. If your cycles are irregular or if you conceived via IVF, Lunara also offers options to input your conception date or embryo transfer date.
Pregnancy Week Calculator by Due Date
Once you've estimated your due date, the next step is understanding what stage of pregnancy you’re currently in. Lunara also works as a pregnancy week calculator by due date, helping you track your pregnancy week by week. This means you can follow your baby's development, anticipate important milestones, and plan necessary tests and appointments accordingly.
With the due date calculator week by week, you'll gain valuable insights into fetal growth, maternal changes, and what to expect each week, all the way through to delivery.
How Accurate is the Due Date?
Many people wonder "how accurate is the due date?" The truth is, due dates are estimates based on averages. While the 40-week timeline is standard, only about 4% of babies are actually born on their due date. Most arrive within a two-week window before or after.
Lunara offers one of the most reliable estimation methods by using the standard medical model. It’s a useful guide for planning appointments, arranging maternity leave, and preparing for childbirth.
Key Takeaways on Pregnancy Due Date Calculator
● Lunara’s pregnancy due date calculator gives you an estimated due date based on the first day of your last period or known conception date.
● Most pregnancies last around 40 weeks. But every pregnancy is unique, so your baby might arrive a little earlier or later.
● You can also use a pregnancy week calculator by due date to track your baby’s growth week by week.
● If you’re thinking, “How do I calculate my due date?” or “If I got pregnant today, when would I be due?” — our tool gives you a quick answer.
● Your doctor may use an ultrasound to calculate your pregnancy due date more accurately and guide your prenatal care.
● The due date pregnancy calculator is a helpful guide, but it doesn’t replace medical advice. Always follow up with your healthcare provider for confirmation.
Quickly Find Out What Month You’re Due!
Predicting your due date isn’t an exact science. However, assuming a 40-week pregnancy and a regular 28-day cycle:
● If you conceived in January, your baby may be due in October
● If you conceived in February, your baby may be due in November
● If you conceived in March, your baby may be due in December
● If you conceived in April, your baby may be due in January
● If you conceived in May, your baby may be due in February
● If you conceived in June, your baby may be due in March
● If you conceived in July, your baby may be due in April
● If you conceived in August, your baby may be due in May
● If you conceived in September, your baby may be due in June
● If you conceived in October, your baby may be due in July
● If you conceived in November, your baby may be due in August
● If you conceived in December, your baby may be due in September
Your due date can feel definite, but it's more of an estimate. It may vary depending on your cycle length and exactly when in the month you conceived.
Similarly, research shows that very few births happen exactly on the due date. While 40 weeks is the average length of pregnancy, it's typical for babies to be born anytime between 37 and 42 weeks. This means your baby might arrive a little earlier or later than expected, which could shift your estimated birth month.
If you’d like a more accurate timeline, use the Lunara pregnancy due date calculator. And if your cycles are irregular, your doctor may calculate your due date using other clinical data.
Other Ways of Calculating Your Due Date
There isn’t just one way to estimate a due date. Here are a few alternatives that may work depending on your unique circumstances:
Conception date
If you know the exact date you conceived, you can calculate your due date by adding 266 days. This is useful for those who track ovulation or have a known fertility event.
IVF transfer date
For IVF pregnancies, due dates are calculated from the day of embryo transfer. For example, with a Day 5 embryo transfer, your due date is the transfer date plus 261 days. Lunara includes IVF-specific options to ensure accuracy.
First ultrasound
When menstrual dates are unclear, early ultrasounds (typically 8–12 weeks) are highly accurate at dating a pregnancy. If your LMP is unknown or your cycle is irregular, ultrasound is often preferred.
Cycle length adjustments
If your cycle isn’t the standard 28 days, modifying your LMP-based calculation according to your actual cycle length offers a more tailored result.
Each of these methods is supported within the Lunara pregnancy due date calculator, giving you flexibility and reassurance no matter how your pregnancy began.
Can a Pregnancy Due Date Change?
Yes, and it’s quite common. If your initial estimated due date was based on LMP but your scan suggests a different gestational age, your doctor may update your due date. Factors such as irregular cycles, uncertain LMP, or early fetal growth patterns can all influence the calculation.
Wondering "can a pregnancy due date change?" is perfectly normal — and the answer is yes. But rest assured: these changes are made to provide the most accurate care possible.
Estimate Your Due Date Today with Lunara
Whether you’re newly pregnant or just curious about your pregnancy timeline, the Lunara pregnancy due date calculator makes it easy to estimate your due date in seconds. Simply enter the first day of your last period, and our intuitive tool will give you a clear timeline to help you plan appointments, prepare your maternity leave, and anticipate your baby's arrival.
So if you’re asking yourself things like calculate my due date, how to find out your due date, calculate my pregnancy due date, or even if I got pregnant today when would I be due — Lunara is your go-to tool.
Try it today and take the guesswork out of your pregnancy journey!