Due Date Calculator: Pregnancy Delivery Date Estimation (LMP, Conception, IVF & Ultrasound)
This due date calculator estimates your baby's expected delivery date (EDD) using the method that fits your situation: the first day of your last menstrual period (LMP), your conception date, an ultrasound result or an IVF embryo transfer date. It also shows your gestational age, trimester, conception window, days remaining and key pregnancy milestones in one simple timeline.
Quick answer: add 280 days (40 weeks) to the first day of your last period. For example, a last period that started on January 10, 2026 gives an estimated due date of October 17, 2026.
How to Calculate Your Due Date
Doctors and midwives use several methods, and the right one depends on what you know. The calculator uses the standard formulas below.
| Method | Calculation | Best used when |
|---|---|---|
| LMP | LMP + 280 days, adjusted for cycle length | You know your last period date and have a fairly regular cycle |
| Conception | Conception date + 266 days (38 weeks) | You know the date of conception or ovulation |
| Ultrasound | Scan date + (280 days − gestational age at the scan) | You have a dating scan, ideally in the first trimester |
| IVF, Day 5 transfer | Transfer date + 261 days | A blastocyst was transferred |
| IVF, Day 3 transfer | Transfer date + 263 days | A Day 3 embryo was transferred |
The LMP method assumes a 28-day cycle with ovulation around day 14. If your cycle is longer or shorter, the calculator adjusts the date: a 32-day cycle moves the due date 4 days later, and a 24-day cycle moves it 4 days earlier.
How Accurate Is a Due Date?
A due date is an estimate, not an exact day. Only about 4 to 5 percent of babies are born on their due date, and most arrive within about two weeks before or after it. An ultrasound in the first trimester is generally the most accurate way to date a pregnancy, and your healthcare provider may adjust your due date after a scan if the measurements differ from the LMP date. Twins and other multiples are often born earlier, commonly around 36 to 37 weeks.
Trimesters and Pregnancy Milestones
The first trimester covers weeks 1 to 12, the second weeks 13 to 27, and the third week 28 until birth. Beyond your due date, the calculator shows when your first trimester ends, the usual time of the anatomy scan (about 20 weeks), the viability milestone (about 24 weeks), when early term (37 weeks) and full term (39 weeks) begin, and a progress bar for how far along you are.
Why Knowing Your Due Date Helps
An estimated due date helps you plan prenatal appointments, follow your baby's development stage by stage, prepare for the changes in each trimester, organize your hospital bag and birth plan, and talk to your provider about nutrition and supplements. To count the weeks and days between any two dates, use the date calculator, and for tracking your cycle you can try the period calculator. The pregnancy calculator can help with the weeks that follow.
This calculator gives an estimate for general information and is not medical advice. Confirm your due date with your doctor or midwife, and contact them if you have any concerns about your pregnancy.
Who Should Use This Calculator?
Expecting parents tracking their pregnancy, couples trying to conceive, people going through IVF or fertility treatment, healthcare students, doctors and midwives who need a quick estimate, and pregnancy bloggers can all use it. It is designed to be simple enough for personal use while following standard pregnancy dating methods.
How to Use This Due Date Calculator
Choose your method
Select LMP, Conception, Ultrasound or IVF Transfer.
Enter the date
Add the date that matches your method, such as the first day of your last period.
Adjust the details
Change your cycle length if it is not 28 days, or add the weeks and days from your scan.
Click "Calculate Due Date"
See your estimated due date, gestational age, trimester, conception window and milestones.