About PregnancyCalc
PregnancyCalc turns the pregnancy calendar into arithmetic you can check — dates, weeks, and ranges with their sources.
Pregnancy dating confuses everyone at first: you are "four weeks pregnant" roughly two weeks after conception, the due date is an average drawn from a 250-year-old rule plus modern ultrasound, and trimester boundaries move depending on which source you read. The math is simple; the conventions just need showing.
Our calculators implement the published methods — Naegele's rule with cycle-length adjustments, obstetric week counting, and the Institute of Medicine's weight-gain ranges by pre-pregnancy BMI — and label every assumption so you know exactly where the estimate ends and your clinician's dating begins.
We are educators, not clinicians. Nothing here replaces prenatal care, and nothing here is a medical judgment. The tools exist to make the calendar legible between appointments.
What makes PregnancyCalc different
- Your numbers never leave your browser. Every calculator on PregnancyCalc runs entirely on your device. We never see, store, or transmit the figures you enter — there are no accounts and no server-side processing of your inputs.
- Published methodology. Each calculator page explains the exact formula it uses and the assumptions behind it, so you can check our work or reproduce it in a spreadsheet.
- Free, forever, without a paywall. PregnancyCalc is supported by advertising. There is no premium tier, no email gate, and no upsell.
Independence
PregnancyCalc is an independent educational project. We are not affiliated with, endorsed by, or acting on behalf of any government agency, lender, insurer, or the organizations whose formulas and public data we reference (such as ACOG and IOM public clinical guidance). All trademarks and referenced standards belong to their respective owners.
Questions, corrections, or suggestions are genuinely welcome — get in touch.