Due Date Calculator
Free pregnancy due date calculator. Estimate your due date, current gestational age, trimester and conception date from the first day of your last menstrual period.
Your Dates
Select the first day of your last menstrual period to estimate your due date.
How It Works
Enter your last period date
Select the first day of your last menstrual period (LMP) from the date picker.
Adjust your cycle length
Set your average cycle length if it differs from the standard 28 days, so ovulation and the due date are estimated more accurately.
Review your estimates
See your estimated due date, how many weeks along you are, your trimester, the estimated conception date and days remaining.
A due date is an estimate of when your baby is most likely to arrive, traditionally set at 40 weeks (280 days) from the first day of your last menstrual period. Because ovulation timing varies, the estimate is refined using your average cycle length, and an early ultrasound can adjust it further.
This calculator gives you your estimated due date, current gestational age, trimester, estimated conception date and the days remaining. These figures are general estimates for information only and are not medical advice — always confirm your dates and care plan with a doctor or midwife.
Frequently Asked Questions
How is my due date calculated?
The most common method, Naegele’s rule, estimates the due date as 280 days (40 weeks) from the first day of your last menstrual period. If your cycle is longer or shorter than 28 days, the calculator shifts the due date by the difference, because ovulation happens earlier or later.
What is gestational age?
Gestational age is how far along your pregnancy is, counted in weeks and days from the first day of your last period — not from conception. That is why pregnancy is described as roughly 40 weeks even though fertilisation happens about two weeks after your period starts.
When does each trimester begin?
The first trimester runs from week 0 up to the end of week 12, the second trimester covers weeks 13 through 26, and the third trimester runs from week 27 until birth. This calculator labels your current trimester based on your gestational age.
How accurate is an estimated due date?
Only about 1 in 20 babies are born on their exact estimated due date; most arrive within two weeks either side. An early ultrasound usually gives a more precise estimate than the last-period method, so always confirm dates with your healthcare provider.
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