Pregnancy Due Date Calculator: LMP, Conception and IVF
Estimate a due date using your last period, a known conception date, or a day-3 or day-5 embryo transfer.
Your inputs
Choose the units and assumptions that match your data. Example inputs are illustrative.
Your result
Enter your values, then choose Calculate.
Results are calculated in your browser. Display rounding does not change the underlying calculation.
Calculation breakdown
Method, assumptions and worked example
How it works
The last-period method adds 280 days and adjusts by cycle length minus 28. A known conception date adds 266 days. Day-3 and day-5 embryo transfer dates add 263 and 261 days respectively, accounting for embryo age. A date of intercourse is not necessarily a conception date.
Worked example
For a last period beginning 1 January 2026 and a 28-day cycle, the estimated due date is 8 October 2026.
Using the result
This is an estimate. Irregular cycles and uncertain dates reduce reliability; ultrasound and maternity care can revise dating. For IVF use the actual transfer date and embryo age supplied by the clinic. The tool does not establish pregnancy viability or provide medical scheduling.
Frequently asked questions
Is the due date my exact delivery day?
No. It is an estimated reference date, and births occur before and after it.
Which date do I enter for IVF?
The embryo transfer date, with the correct day-3 or day-5 option.
Method review and references
Formula and content reviewed on 10 October 2026. Worked examples are hypothetical. Methods and assumptions are explained on each page. Health estimates are not clinical measurements; symbolic tools are for entertainment.