Methodology
Every DueDateLab calculator ships with a dedicated methodology page. Each one documents the exact formula, input validation rules, source citations, authorship, and a full version history. The goal is simple: anyone should be able to verify how a result was produced, from which sources, and by whom.
Why publish this
Most online pregnancy calculators do not disclose their formulas, their source guidelines, or the clinician (if any) who reviewed them. That makes it hard to trust the output and almost impossible to cite the result correctly elsewhere. DueDateLab takes the opposite position. If a calculator is worth trusting, the method behind it is worth reading.
Available methodology pages
- Due Date Calculator, Naegele's rule, conception-date method, ultrasound adjustment thresholds (ACOG 700), input validation, and delivery windows.
- Conception Calculator, LMP method, EDD reverse method, and IVF transfer-date method for estimating the date of conception.
- Ovulation Calculator, luteal-phase-anchored ovulation prediction from LMP and cycle length, 6-day fertile window per Wilcox 1995 (NEJM), and 3-day peak-fertility window.
- Baby Percentile, LMS method (Cole & Green 1992) applied to WHO standards (0 to 24 months) and CDC growth charts (2 to 20 years) with the WHO-to-CDC transition at 24 months per MMWR 2010.
- Sleep Needs by Age, AAP-endorsed AASM 2016 (Paruthi) bands for ages 4 months to 18 years, plus NSF 2015 for newborns where AASM is silent.
- Names, popularity and trend data sourced directly from the U.S. Social Security Administration. SSA suppression handling, sex-series labelling, hyphen and space tabulation rules. Pages do not include meanings, origins, or pronunciation.
- Chinese Gender Chart, lunar-age conversion, chart lookup, and accuracy evidence. This tool is categorized as entertainment, not medical.
Editorial standards
- Every medical claim is cited to a named primary source: ACOG, NICE, NHS, AAP, WHO, CDC, or peer-reviewed journals.
- Every calculator's methodology page is linked from the calculator itself.
- Methodology pages are re-reviewed on a quarterly cadence.
- Every medical methodology page is bound strictly to its primary sources and carries an editorial byline on behalf of the DueDateLab Editorial team. Each methodology page includes a full source list and cites its governing primary sources. Entertainment tools (such as the Chinese Gender Chart) do not require clinical review and are clearly labeled as non-medical.
- No diagnostic or treatment recommendations are made anywhere on DueDateLab.
- Calculator inputs are processed in the user's browser and are never transmitted.