Pregnancy Due Date Calculator
When is my baby due? Estimate your pregnancy due date from the first day of your last period and average cycle length, a well-supported ovulation date, a conception or documented fertilization date, or pregnancy weeks written on a dated record or dating scan.
Your due date is an estimate used to organize pregnancy timing. It is not a guaranteed birth date.
Free browser-based pregnancy and preconception calculators with transparent methods, sources, assumptions, and limitations.
How to use this due date calculator
- Start with the first day of your last period when it is reliable. The default 28-day cycle can be adjusted within the supported 21–35-day range.
- Open the other options only for a well-supported ovulation date, a known conception or documented fertilization date, or completed pregnancy weeks and days from a dated record.
- Read the estimated due date, pregnancy weeks, trimester, calculation path, and timeline together. You can also check pregnancy weeks on another date.
If you already have an established due date and only need pregnancy weeks, use the Gestational Age Calculator. If you have an embryo transfer record, use the IVF Due Date Calculator.
Already have a due date and want an around-date conception estimate? Use the Conception Date Calculator.
How accurate is a pregnancy due date estimate?
An estimated due date (EDD) is a shared reference for pregnancy timing, not a prediction of the exact day labor or birth will occur. An uncertain last menstrual period (LMP) or substantial cycle variation can reduce the usefulness of a simple calendar estimate.
A dating scan and the pregnancy record may establish or confirm dating. If your care team has established an EDD, use that date for care rather than repeatedly replacing it with online calculations.
This calculator does not interpret ultrasound measurements, diagnose a pregnancy, or decide whether clinical redating is appropriate.
How pregnancy dating and due dates work
Read the pregnancy dating guide for the 280- and 266-day calendar methods, cycle examples, completed weeks and days, ultrasound context, clinical dating boundaries, and official source mapping.
Frequently asked questions
- How do I calculate my due date from my last period?
- Enter the first day of your last period and your usual or average cycle length. The standard 28-day model adds 280 days; a supported 21–35-day cycle shifts that estimate by the difference from 28 days.
- What if I do not know my last period or my cycles are irregular?
- Do not guess a date you do not remember. Substantial cycle variation or an uncertain last-period date can make a simple calendar estimate less useful. A dated pregnancy record or an established clinical due date may be a better reference.
- Can I calculate my due date from a conception date?
- Yes, when the conception or fertilization date is genuinely known or well supported. The calculator adds 266 days. Do not use an intercourse date as a confirmed conception or fertilization date.
- Can I calculate my due date from an ovulation date?
- Yes. The calculator adds 266 days to the ovulation date entered. An app prediction, symptom, or home test may still estimate rather than establish the exact ovulation date.
- Can I calculate a due date from pregnancy weeks on a dating scan?
- Yes, when the report states completed pregnancy weeks, additional days, and the scan date together. Enter those recorded values. This calculator does not interpret ultrasound measurements or decide whether a pregnancy should be clinically redated.
- How accurate is a due date calculator, and will my baby be born that day?
- A due date is a pregnancy-timing estimate, not a guaranteed birth date. The usefulness of a calendar estimate depends on the reliability of the starting record, and an established due date from your care team remains the priority for care.
- Should IVF pregnancies use this calculator?
- Use the IVF Due Date Calculator when you have an embryo transfer date and documented embryo age. IVF dating uses that treatment record rather than the ordinary last-period, ovulation, or conception paths on this page.