The estimated due date uses Naegele's rule, a long-standing obstetric formula: first day of your last menstrual period (LMP) plus 280 days (40 weeks) — the standard method used to estimate a due date when the exact conception date isn't known.
Ovulation, and the conception date estimate shown alongside it, is calculated as LMP plus (your cycle length minus 14 days) — based on the typical pattern where ovulation occurs roughly 14 days before the next period, adjusted for your actual cycle length rather than assuming everyone has an identical 28-day cycle.
Gestational age is calculated as the whole weeks and leftover days elapsed from your LMP to today's date — the standard way pregnancy progress is measured and communicated by healthcare providers. All of these figures are estimates based on population averages, not a personalized medical assessment, and actual due dates and ovulation timing can vary meaningfully between individuals.
It's a widely used standard estimate, but only about 4-5% of babies are actually born on their exact calculated due date — most arrive within a couple of weeks either side. It's a useful planning estimate, not a precise prediction.
Because ovulation timing relative to your period depends on your cycle length — a shorter or longer cycle than the typical 28 days shifts when ovulation likely occurred, which affects the conception date estimate.
Gestational age counts from the first day of your last menstrual period, which is about two weeks before conception actually occurs. This is the standard convention used by healthcare providers, even though it means gestational age runs about two weeks ahead of true fetal age from conception.
No — this provides a general estimate based on standard formulas and population averages. Your healthcare provider may adjust your due date based on an ultrasound or other clinical information specific to your pregnancy.
