Pregnancy Due Date Calculator

How the two date methods work

This calculator estimates a calendar due date from either the first day of your last menstrual period (LMP) or a date you enter as conception. The LMP method starts from the first day bleeding began, not the last day of the period. Its default model adds 280 days, or 40 weeks, then adjusts for the cycle length you enter. The conception method adds 266 days to the entered date. These are date calculations; neither method confirms when ovulation or conception actually occurred.

For example, an LMP of January 1, 2026 with a 28-day cycle gives an estimated due date of October 8, 2026. With a 32-day cycle, the tool adds four more days, giving October 12. The cycle adjustment applies only in LMP mode. A longer or shorter cycle shifts the model's date; it does not measure your ovulation.

What the result panel shows

Alongside the estimated due date, the result includes an estimated conception date, gestational age in weeks and days, days remaining, and a progress percentage. Gestational age is counted from the date 280 days before the calculated due date, using the current calendar date. Days remaining is shown as zero once the estimated due date has passed, and progress is capped at 100%; those display limits do not describe labor, fetal development, or pregnancy status.

The panel also shows the due date's weekday, zodiac sign, Chinese zodiac and lunar-calendar date. These are calendar or cultural details, separate from the medical date estimate. The lunar date is displayed using Chinese calendar wording, even when the surrounding controls are in English.

Choose a starting date and read the estimate

1. Select the date basis

   Choose the LMP option if you know when your last period began. Choose conception date only if you have a date you want to use as the estimated conception day. The page does not offer fields for ultrasound dating, embryo age, or transfer date.

2. Enter the date and, if relevant, cycle length

   For LMP, enter the first day of the last period. The cycle field starts at 28 days; change it to your usual cycle length if that is known and reasonably consistent. In conception mode, only the entered date is used and the cycle field is hidden.

3. Review or share the displayed result

   The estimate updates when the date or cycle length changes. Use the copy controls beside individual results, or the share option to preserve the selected calculation inputs. The Clear control resets the date to today rather than leaving it blank.

Questions about inputs and timing

When a calendar estimate is not enough

This result is an estimate, not a diagnosis or a confirmed gestational age. It cannot tell you when labor will begin, and a due date is not a promise that birth will occur on that day. Use the date established in your prenatal record for care decisions.

• If your periods are irregular, you are unsure of the LMP, or the date is only a guess, the input may not reflect the pregnancy's actual timing. Ask a qualified prenatal care professional how your dates should be assessed.
• ACOG identifies first-trimester ultrasound as the most accurate method to establish or confirm gestational age. For a pregnancy from assisted reproduction, clinical dating uses the embryo's age and transfer date; this calculator does not support those inputs.
• The conception-date option simply adds 266 days to the date entered. It does not validate that date. Likewise, changing cycle length changes the arithmetic but does not verify ovulation.
• The tool's progress and days-remaining displays are capped values, not clinical assessments. Its lunar-calendar field is shown in Chinese wording and is not a medical result.