Pregnancy Due Date Calculator
Estimate a pregnancy due date from the last menstrual period with a cycle-length adjustment.
Your results
- Estimated due date
- 2027-07-10
- Estimated conception
- 2026-10-17
- Completed gestational weeks
- 0
- 39-week full-term milestone
- 2027-07-03
Calculations run in your browser. Results are estimates where described below.
How the calculation works
Estimated due date = first day of last period + 280 days + (cycle length − 28). Gestational weeks use the adjusted dating origin.
Worked example
Last period 1 January 2026 and a 28-day cycle gives an estimated due date of 8 October 2026.
Assumptions and limits
For reasonably regular cycles. Ultrasound and clinical assessment can change dating. The 39-week date marks full term; 37 weeks is early term. This calculator does not confirm pregnancy.