Pregnancy Trimester Calculator
Enter your due date to see the start and end dates of each trimester.
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 your estimated due date. The calculator shows the start and end dates of each trimester from your estimated LMP.
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.