Conception Calculator

Method

As of Date (optional)

Defaults to today (UTC). For display context only.

LMP (Last Menstrual Period)

Average Cycle Length (days)

Typical range 21–45; default 28.

Conception Calculator – Quick Cheat Sheet

LMP method: Ovulation ≈ LMP + (cycle − 14). Conception ~ ovulation day (±1 day). Fertile window = ovulation −5 to +1.
EDD method: Conception ≈ EDD − 266 days (~38 weeks). Fertile window centered on that date.
Ovulation method: Conception = provided ovulation date; fertile window = ovulation −5 to +1. Back-calculates LMP and EDD.
Generalized EDD from LMP: EDD ≈ LMP + (252 + cycle) days (28-day cycle → +280 days).
Cycle length typical range: 21–45 days; longer cycles shift ovulation later.
Limits: These are averages; individual variation is common. Ultrasound dating may differ.

Notes & assumptions

Strict YYYY-MM-DD parsing in UTC to avoid timezone/DST issues.
“As of Date” is optional and used only to timestamp output context.
This tool does not store or upload data; it runs entirely in your browser + server calculation.