Use this free pregnancy calculator (due date calculator) to estimate your due date, current pregnancy week, conception date, and trimester milestones based on your last menstrual period or conception date.
How to use this calculator
Select your calculation method: last menstrual period (LMP) or conception date.
Enter the date using the date picker.
Adjust your average menstrual cycle length (default is 28 days).
Read your estimated due date, current gestational age in weeks and days, current trimester, and countdown.
Formula & method
Naegele's Rule & Gestational Age Calculation
Due Date = LMP + 280 days + (Cycle Length − 28 days)
LMP = First day of last menstrual period. Standard gestational length is 280 days (40 weeks).
Example
For an LMP of Jan 1 with a 28-day cycle: Due Date = Jan 1 + 280 days = Oct 8.
Key insights
Full-term pregnancy lasts approximately 40 weeks (280 days) from the first day of the last menstrual period (Naegele's rule).
Only about 4% of babies are born on their exact estimated due date; most arrive within 2 weeks before or after.
Conception typically occurs roughly 14 days after the first day of your last period in a standard 28-day cycle.
The first trimester spans weeks 1–12, the second trimester weeks 13–26, and the third trimester weeks 27–40.
How to interpret your result
Estimated Due Date (EDD)
The projected date of birth based on standard 40-week gestational age calculations.
Gestational Age
The age of the pregnancy measured in weeks and days from the start of the last menstrual period, not actual fetal age.
Trimester Status
Identifies your current stage of pregnancy to guide prenatal care and developmental expectations.
Frequently asked questions
How is the due date calculated?
The due date is calculated by adding 280 days (40 weeks) to the first day of your last menstrual period, adjusted for cycle length.
How accurate is the due date calculator?
An ultrasound scan performed in the first trimester is the most accurate method to confirm gestational age and due date.
Does this tool work as a conception calculator?
Yes. The calculator estimates your conception date as approximately 14 days after your last period.