Short version: use the calculators and guides here, and these terms apply to you. Longer version follows, because a due date site owes you more than a boilerplate paragraph.
Punch a date or a number into the due date, pregnancy, ovulation, conception, conception date, hCG doubling, weight gain, trimester, period, implantation or gestational age tool, and you get arithmetic run against a named method, Naegele's rule, ACOG's redating guidance, or one of the other sources catalogued on editorial standards. That output is a planning number. It is not a diagnosis, it is not a due date any hospital owes you over your own provider's dating, and it does not stand in for an exam, bloodwork, or a scan. This site has no clinical staff and is not claiming otherwise anywhere on it.
Every redating threshold, every term-length category, traces to a specific ACOG opinion or CDC page, dated on the editorial standards page rather than presented as timeless fact. We check those sources against the live ACOG and CDC pages a couple of times a year, and when one gets reaffirmed or replaced, the affected calculator and its citation get updated to match.
The site is handed to you as it is, with no guarantee that any given result lines up with your actual due date or timeline. A formula can match its published source exactly and still miss an irregular cycle it was never told about, a health condition, or a scan it has no way of seeing, which is the entire reason every guide here points back to your own provider for confirmation rather than treating a calculator output as settled.
We are not on the hook for a missed appointment, a scheduling decision, or any other consequence of trusting a number from this site over your provider's own dating, or for anything that happens after you click through to a third-party site from here. What happens with your pregnancy, and the timing decisions around it, stays between you and your provider; treat this site as a way to sharpen the questions you bring to that conversation.
Ads through Google AdSense and a small set of affiliate links cover the cost of keeping this site running; a purchase through one of those links can earn a commission at no cost to you, and none of that revenue touches which formula a calculator runs.
We update this page as the site itself changes, and the date at the top marks the last revision. Keep using the site after that and the current version is the one that applies.