🤰 Due Date Calculator

Quickly estimate your baby's due date based on the first day of your last menstrual period (LMP). This tool assumes a typical 40-week pregnancy.

Important: Every pregnancy is unique. Your actual delivery date may differ. Use this calculator as a guideline only.

Pregnancy is divided into three trimesters:

  • First trimester: weeks 1–12
  • Second trimester: weeks 13–26
  • Third trimester: weeks 27–40

Regular prenatal care is essential. Contact your healthcare provider for personalized advice and monitoring.

How your due date is calculated

This calculator uses Naegele's rule, the standard method used by clinicians: it adds 280 days (40 weeks) to the first day of your last menstrual period (LMP) to estimate your due date (EDD — estimated date of delivery).

Because it assumes a regular 28-day cycle with ovulation on day 14, your true date can shift if your cycle is longer or shorter. An ultrasound dating scan is more accurate, especially in the first trimester. Only about 1 in 20 babies arrive exactly on the estimated date — most are born within the two weeks either side.

Pregnancy trimester timeline

TrimesterWeeksRoughly
First1–12Months 1–3
Second13–26Months 4–6
Third27–40Months 7–9

Frequently asked questions

How is the due date calculated from my last period?

Add 280 days (40 weeks) to the first day of your last menstrual period (LMP). This is Naegele's rule and is the same starting point most clinicians use before refining the date with an ultrasound.

What does EDD mean?

EDD stands for Estimated Date of Delivery — the projected date your baby is due, about 40 weeks from your last menstrual period. It is an estimate, not a guarantee.

How accurate is an LMP-based due date?

It is a good estimate for regular 28-day cycles, but can be off if your cycle is irregular. A first-trimester dating ultrasound gives a more accurate due date. Most births occur within two weeks before or after the EDD.

Can I calculate my due date from the conception date?

Yes — conception typically occurs about two weeks after the start of your last period, so a conception-based estimate adds roughly 266 days to the conception date. This tool uses the LMP method, which is the more common clinical standard.

Related calculators