Use the free Conception Calculator on ToolVexa to estimate a conception date and a due date from the first day of the last menstrual period.
How to Use
Enter the first day of the last menstrual period, then press Calculate. The result shows an estimated conception date and an estimated due date.
Formula in Plain Words
The estimated conception date is the LMP date plus 14 days, assuming ovulation about two weeks after the period starts. The estimated due date is the LMP date plus 280 days, or 40 weeks.
Worked Example
For an LMP of 1 January 2026, the estimated conception date is 15 January 2026 and the estimated due date is 8 October 2026.
FAQs
Is this exact?
No. It is an estimate based on a typical 28-day cycle. Real ovulation and pregnancy length vary.
What if my cycle is longer or shorter?
Then the estimate may be a few days out. An ultrasound in early pregnancy gives a more personal estimate.
Does this replace medical advice?
No. Use it for general planning only and speak to a clinician for personal advice.