Estimate conception date based on due date or LMP.
This guide explains how simple online tools work, what they tell you, and how to interpret results so you feel confident about timing, health, and next steps.
A due date calculator uses either the first day of your last menstrual period or conception data to estimate an expected birth date. A pregnancy calculator often adds context: average fetal development milestones, trimester breakdowns, and when important screenings are typically offered. Together, these tools let you plan appointments, travel, and work adjustments with less guesswork. If you prefer personalized results, enter an accurate cycle length and the date you think conception happened.
If you know the conception date, many tools will show exactly how many weeks and days you are.
If you only know your last period, the tool converts that to gestational age (how far along am I) using standard medical dating. Use these results to understand when ultrasounds will be most accurate and when common symptoms typically appear.
If you’re asking “when did I conceive?” or searching for a “when did I get pregnant exactly calculator,” a conception date calculator narrows the window based on ovulation and intercourse dates. Keep in mind that sperm can survive up to five days, and the egg is fertile for about 12–24 hours, so conception can occur several days after sex. For women tracking health and fitness alongside pregnancy plans, tools like a fitness and health calculator for weight loss can be helpful before conception; maintaining a healthy weight supports fertility and reduces certain pregnancy risks. Always confirm any online estimate with your clinician, who may use an early ultrasound to provide the most reliable dating.