Pregnancy tools
Due Date Calculator
Congratulations on your pregnancy! It is an exciting time, and we know one of the first questions on your mind is, “What’s my due date?” Use the calculator below to estimate your due date, see how far along you are, and preview the milestones ahead.
Your estimated due date
This calculator gives an estimate only and is not medical advice. Every pregnancy is different, and your provider will confirm your due date, usually at your first ultrasound.
How your due date is calculated
The standard method, the one most providers use, is called Naegele's rule: your estimated due date is 280 days, or 40 weeks, from the first day of your last menstrual period. That may sound strange, because it means the count starts about two weeks before you actually conceived. In those first two weeks your body is preparing to ovulate, so by the time a home test turns positive you are usually already considered 4 weeks pregnant.
Our calculator supports five ways to arrive at the date, depending on what you know:
- Last period: the first day of your last period plus 280 days, adjusted if your cycle runs longer or shorter than 28 days.
- Conception date: if you know when you ovulated or conceived, your due date is that date plus 266 days.
- IVF transfer: the most precise starting point of all. A day 5 embryo transfer adds 261 days, and a day 3 transfer adds 263 days.
- Ultrasound: enter your scan date and the gestational age from the report, and we count forward from there. Early ultrasounds are the most accurate dating method available.
- I know my due date: already have a date from your provider? Work backward to see how far along you are and when each milestone lands.
How accurate is a due date calculator?
Here is the honest answer: a due date is a well-informed estimate, not an appointment. Only about 1 in 20 babies is born on the due date itself, and most arrive within a week on either side. Babies develop at their own pace, and every pregnancy is unique.
Your provider will confirm or adjust the date at your first prenatal visit, usually based on an early ultrasound. Measurements taken in the first trimester give the clearest picture of gestational age, which is why a scan sometimes moves a due date by a few days. That is normal and nothing to worry about. In the meantime, the estimate is a wonderful planning target: it tells you which week you are in, what is coming next, and how much time you have to get ready.
Your pregnancy, trimester by trimester
First trimester: weeks 1 to 13
The foundation weeks. Your baby's heart starts beating around week 6, and by the end of the trimester all the major organs have formed. You may be tired and queasy while your body does this enormous work, so be gentle with yourself. Your first prenatal visit and dating ultrasound usually happen during these weeks.
Second trimester: weeks 14 to 27
Often the most comfortable stretch. Energy tends to return, the bump makes its debut, and somewhere around weeks 18 to 22 you will feel those first flutters and have your anatomy scan. This is also a smart time to start thinking about feeding plans and to look into getting your breast pump through insurance, since coverage almost always includes a pump before your baby arrives.
Third trimester: week 28 to birth
The home stretch. Baby is growing fast, appointments get more frequent, and the nesting instinct kicks in. If you have not ordered your pump yet, now is the time, so it is washed, assembled, and ready before your due date. Not sure which pump fits your life? Our breast pump comparison chart lines them up side by side.
Want to read more while you count down? Start with When is my baby due? and 10 things to do when you find out you're expecting on our blog.
Due date questions, answered
How do I calculate my due date?
Count 280 days, or 40 weeks, from the first day of your last menstrual period. That is the standard method providers use, known as Naegele's rule. If your cycles are longer or shorter than 28 days, the estimate shifts by the difference, which our calculator handles for you.
What if my cycles are irregular?
The last-period method assumes a fairly regular cycle, so it gets less reliable when yours varies a lot. If you know your conception or ovulation date, use that method instead. A first-trimester ultrasound gives the most accurate dating of all, and your provider will use it to confirm or adjust your due date.
How many weeks pregnant am I?
Pregnancy weeks are counted from the first day of your last period, not from conception. That means you are already about 4 weeks along by the time you miss a period. Enter your dates above, or pick "I know my due date" if your provider already gave you one, and the calculator shows exactly how many weeks and days along you are.
Can my due date change?
Yes. Your provider may adjust your due date after your first ultrasound, where measurements of the baby give a more precise picture of gestational age. An adjustment of a few days to a week is common and completely normal.
How accurate are due date calculators?
A due date is an estimate, not an appointment. Only about 1 in 20 babies arrives on the due date itself, and most are born within a week on either side of it. Treat the date as a planning target, and let your provider fine-tune it as your pregnancy progresses.
When should I order my breast pump through insurance?
Most insurance plans cover a breast pump before your baby arrives, and many moms order during the second or third trimester so the pump is ready and waiting. Checking your coverage takes just a few minutes and there is no cost to find out what your plan includes.
Start thinking about your breast pump
Most insurance plans cover a breast pump before your baby arrives. Check your coverage now so your pump is ready and waiting when you are.
Content reviewed by The Breastfeeding Shop team. Last updated July 2026.