Estimate your due date from the first day of your last period and see how far along you are today.
Runs in your browser — nothing is uploaded
Most due dates are estimated with Naegele's rule: add 280 days, or 40 weeks, to the first day of your last menstrual period. The rule assumes a 28-day cycle with ovulation around day 14, so the calculator adjusts the date when your cycles are longer or shorter.
Your gestational age is counted from that first day, which is why a pregnancy is measured as 40 weeks even though conception happens about two weeks later. The calculator shows your weeks and days today and the trimester you are in.
Only about 5 percent of babies arrive on their due date. Most arrive within two weeks either side. Ultrasound in early pregnancy is more accurate than the last-period method, and your clinician may adjust the date based on it.
The last-period method is least reliable with irregular cycles. Ask your clinician for an early ultrasound, which measures the baby and gives a better estimate.
The calculator adds one day for each day your cycle exceeds 28 days, and subtracts one for each day shorter. A 32-day cycle moves the due date four days later.
The first trimester runs to about week 13, the second from week 14 to about week 27, and the third from week 28 to delivery. Trimesters are a convenient way to group milestones, not a medical boundary.
No. This is an estimate for planning. Confirm your due date and pregnancy care with a midwife, doctor or other qualified clinician, especially if you have a complicated pregnancy.
No. The dates you enter are used only in your browser and nothing is saved.