Pregnancy Date Estimate Calculator
Use the first day of the last menstrual period, not the day bleeding ended.
Your result
FITNESS & HEALTHEnter your values and select calculate.
On this page How it works & practical examples
How to use the Pregnancy Date Estimate Calculator
Use the first day of the last menstrual period, not the day bleeding ended. This conventional due-date estimate assumes a regular 28-day cycle and places approximate ovulation 14 days after LMP.
The calculation
Worked example
A January 1, 2026 LMP gives October 8, 2026 as the convention-based due date. On May 21, 2026 the elapsed gestational arithmetic is 20 weeks.
Assumptions and limits
Does not determine actual conception, pregnancy viability or delivery timing. Irregular cycles, uncertain LMP and ultrasound dating can change the clinical date; obtain clinical dating rather than treating calendar arithmetic as confirmation.
Common questions
Which inputs should I use?
Use the first day of the last menstrual period, not the day bleeding ended. This conventional due-date estimate assumes a regular 28-day cycle and places approximate ovulation 14 days after LMP.
What does the result exclude?
Does not determine actual conception, pregnancy viability or delivery timing. Irregular cycles, uncertain LMP and ultrasound dating can change the clinical date; obtain clinical dating rather than treating calendar arithmetic as confirmation.