Due Date Calculator with Cycle Length
Enter your cycle length and LMP to adjust your due date for longer or shorter cycles.
100% runs in your browser — no upload, no trackingEstimates only — not medical advice. Confirm all dates and milestones with your doctor or midwife.
How this due date is calculated
Enter the first day of your last period and your usual cycle length. Longer or shorter cycles shift the due date by the difference from a 28-day cycle.
Important note
These calculators use standard formulas — Naegele’s rule (LMP + 280 days) and common IVF conventions (transfer date + 260–263 days). They give estimates for planning only. They are not a substitute for prenatal care, and only your provider can confirm your due date and track your baby’s development.
FAQ
How accurate is my due date?
Only about 4% of babies arrive exactly on the due date. It is an estimate based on your LMP or a scan, and your provider may adjust it after an early ultrasound.
What is Naegele’s rule?
It is the standard method: due date = first day of your last period + 280 days (40 weeks). It assumes a 28-day cycle.
Is my data uploaded?
No. All calculations run in your browser. The dates you enter never leave your device.
Is this medical advice?
No. These are planning estimates. Always confirm dates and milestones with your doctor or midwife.