Pregnancy Due Date Calculator
Estimate your due date and how many weeks pregnant you are from your last period.
Results update as you type.
About this calculator
A pregnancy due date calculator estimates your delivery date using Naegele’s rule: 280 days (40 weeks) from the first day of your last menstrual period (LMP). It adjusts for cycle lengths other than 28 days, and also shows the estimated conception date and how many weeks along you are today. Only about 5% of babies arrive on the exact date.
Because ovulation drives conception, the tool corrects for cycle length. A 32-day cycle is 4 days longer than the standard 28, so it adds those 4 days: the due date becomes LMP + 284 days and the estimated conception moves to about day 18 instead of day 14. It then counts from your LMP to today to show how many weeks and days pregnant you are and which trimester you are in.
Use it early in pregnancy for a working timeline of milestones — the end of the first trimester at week 13, the anatomy scan around week 20, and full term from week 37. The due date is only an estimate: a normal birth can happen anywhere from 37 to 42 weeks, and an early dating ultrasound is more precise. This tool is for information, not medical advice; your provider confirms your dates.
Frequently asked questions
How is the due date calculated?
By Naegele’s rule: add 280 days (40 weeks) to the first day of your last menstrual period. This pregnancy due date calculator also adds the difference if your cycle is longer or shorter than the standard 28 days.
How accurate is the estimated due date?
It is an estimate — only around 5% of babies are born on their due date, and a normal, full-term birth falls anywhere from 37 to 42 weeks. An early ultrasound gives a more precise date.
What if I do not know my last period date?
The LMP method needs that date. If your cycle is irregular or unknown, a dating ultrasound is the standard alternative your provider will use.
How many weeks pregnant am I?
Pregnancy is dated from the first day of your last period, not from conception, so you are counted as about two weeks along at conception. The tool shows your current weeks and days by counting from your LMP to today.
What are the pregnancy trimesters?
The first trimester runs through week 13, the second through week 27, and the third from week 28 to birth. The calculator labels your current trimester from how many weeks along you are.
Does cycle length change the due date?
Yes. Naegele’s rule assumes a 28-day cycle; a longer cycle means later ovulation, so the tool adds the extra days (cycle − 28) to both the due date and the conception estimate.
Can I get a due date from conception or IVF?
This tool works from the last menstrual period. For a known conception date, count 266 days forward; for IVF, the clinic adjusts for the embryo’s age at transfer (for example subtracting 5 days for a blastocyst).
Results are estimates for general guidance only, not financial, medical or tax advice.