Formula
Naegele rule: LMP + 280 days (adjusted for cycle length). Conception path: conception date + 266 days.
Pregnancy Due Date Calculator
Due date, gestational age, and trimester from LMP or conception date with a clear week-by-week style timeline.
Your inputs
About this method
What you get
Estimated due date, gestational age in weeks + days, trimester label, and days remaining.
Limitations
Irregular cycles, IVF dating, and early ultrasound may change the clinical due date. Educational estimate only.
Frequently asked questions
How is the due date calculated?
From the first day of the last menstrual period (LMP) we add 280 days (40 weeks) — Naegele’s rule. Cycle length different from 28 days is adjusted. From a known conception date we add about 266 days (38 weeks).
How accurate is an estimated due date?
Only about 5% of babies arrive on the exact due date. Most births occur within ±1–2 weeks. Ultrasound dating may revise the estimate.
What are the pregnancy trimesters?
Roughly: 1st trimester weeks 0–12, 2nd trimester weeks 13–26, 3rd trimester weeks 27–40+. Exact clinical cut-offs can vary slightly by guideline.
Is this a medical diagnosis?
No. Use TimeVent for planning only. Confirm dating with your clinician or ultrasound.