Due Date Calculator — Quick 8‑Section Guide
1) Core idea
Your estimated due date (EDD) is typically 280 days (40 weeks) from the first day of your last menstrual period (LMP). We adjust for your cycle length and show key milestones.
2) Flow you can trust
- Enter the LMP and select your average cycle length.
- We add 280 days and adjust by (cycleLength − 28).
- See trimester markers, conception estimate, and full‑term date.
3) Sanity checks
- Only ~5% of babies arrive on the exact EDD.
- Normal delivery window: 37–42 weeks.
- Early ultrasound dating often overrides LMP if there’s a mismatch.
4) Shortcuts
- Know conception date? Add 266 days for an EDD estimate.
- No idea on cycle length? 28 days is the standard default.
5) Pitfalls
- Irregular cycles reduce LMP‑based accuracy.
- Uncertain LMP date—prefer early ultrasound.
6) Micro examples
- LMP Jan 1 + 280 days → Oct 8 (28‑day cycle).
- 30‑day cycle: EDD ≈ two days later than the 28‑day rule.
7) Mini‑FAQ
- Can my EDD change? Yes—providers may adjust based on early ultrasound.
- Is this medical advice? No—use for planning; confirm with your clinician.
8) Action tip
Book prenatal care early and plan your first ultrasound around 8–12 weeks to confirm dating.