Due Date Calculator
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Estimated due date (EDD) from your last period using Naegele’s rule adjusted for cycle length.
Rates last reviewed: July 2026
Last menstrual period
Estimated due date
2026-10-17
From LMP 2026-01-10 · 28-day cycle
- EDD (estimate)
- 2026-10-17
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Due date from last menstrual period
The most common due-date formula adds 280 days to the first day of your last menstrual period (LMP) for a 28-day cycle. For other cycle lengths, clinicians adjust: EDD = LMP + 280 days + (cycle length − 28). Only about 5% of babies arrive on the exact EDD.
Ultrasound dating in the first trimester can refine the estimate — especially with irregular cycles. This tool performs calendar math only; your obstetric care team sets the official due date.
Example: LMP January 10, 2026 with a 28-day cycle → EDD October 17, 2026. A 32-day cycle pushes the EDD four days later to October 21, 2026.
Official sources
Rates and formulas in this calculator are based on the documentation below. Platforms change fees — confirm current numbers before pricing or payouts.
Common questions
Why ask for cycle length?
Longer cycles usually mean later ovulation, so the due date shifts forward. The default 28-day assumption may be off if your cycles are irregular.
Is this medical advice?
No. Due dates are estimates. Confirm dating with your clinician and prenatal ultrasound.