A familiar situation
Get an approximate pregnancy due date from the last menstrual period for an initial calendar reference.
How to use this calculator
- Enter first day of last period, usual cycle length.
- Select Calculate to see the answer and its breakdown.
- Keep a scenario, change an input and compare the results.
Use consistent units and check the assumptions below before applying the result.
How pregnancy is calculated
Estimated due date = LMP + 280 days + (usual cycle length − 28 days). Gestational age is counted from the first day of the last menstrual period. An LMP of January 1 with a 28-day cycle gives an estimated due date of October 8.
EDD=LMP+280 days+(usual cycle length−28 days).An LMP of January 1 with a 28-day cycle gives an estimated due date of October 8.
Assumptions & useful context
Approximate dating only; ultrasound and prenatal records may be used to confirm.
Health calculations are estimates for education. They cannot diagnose a condition or replace a clinician’s assessment. Individual needs vary, especially during pregnancy, illness and growth.
Frequently asked questions
Is this due date definitive?
No. A clinician may revise dating based on ultrasound and clinical history.
Does the date predict the exact day of birth?
No; it is an estimate used to track pregnancy timing.