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Pregnancy Due Date Calculator
Estimate your expected delivery date from your last period and cycle length. Change the inputs below and the estimate updates immediately.
Women’s health · calendar estimates
Use your clinician’s confirmed pregnancy dating for medical decisions. This estimate cannot confirm pregnancy or predict the exact day of birth.
Your calculator inputs stay in this page and are not saved or sent to us.
Input
Your numbers
Calculated result
Estimated delivery date
June 21, 2027
Your clinician or dating scan may revise this estimate.
Cycle adjustment
0 days
Compared with the standard 28-day cycle assumption.
Estimate only. Verify important decisions with an appropriate professional or official source.
How to use it
A quick estimate, without the spreadsheet.
Inputs and units
Enter the first day of your last menstrual period and your usual cycle length (21–45 whole days). Use your pre-pregnancy cycle length, not the length of bleeding.
Formula
Estimated delivery date = last menstrual period + 280 days + (cycle length − 28) days. The cycle adjustment assumes ovulation shifts by the difference from a 28-day cycle.
Worked example
A January 1, 2026 last period and a 28-day cycle give an estimated delivery date of October 8, 2026. A 30-day cycle shifts that estimate to October 10.
Assumptions and limitations
An estimated due date is not a promised birth date. Uncertain period dates, irregular cycles and fertility treatment can change pregnancy dating. Use the date confirmed by your maternity clinician or dating ultrasound for medical decisions. These tools do not assess fetal development or diagnose pregnancy. Cycle adjustment is a calendar approximation and is unsuitable for dating an IVF pregnancy.
Health references
Keep calculating