# DueDateLab

> Free, private, evidence-based pregnancy and parenting calculators. Methodology transparency, ACOG and NHS citations, client-side computation.

DueDateLab publishes pregnancy and parenting calculators with full methodology disclosure. Each tool ships with a dedicated methodology page that documents the formula, input validation, source citations, and review history. Calculations run client-side in the browser; inputs are never sent to a server.

## Hubs

- [All Calculators](https://duedatelab.com/calculators/): Index of all DueDateLab calculators across cycle and fertility, pregnancy, and baby and child
- [Cycle and Fertility](https://duedatelab.com/cycle-and-fertility/): Period, ovulation, fertile window, and conception-timing calculators with linked methodology
- [Pregnancy](https://duedatelab.com/pregnancy/): Pregnancy tools and trimester guides, including due date estimates and Chinese Gender Chart (entertainment)
- [Baby and Child](https://duedatelab.com/baby-child/): Baby and child tools plus sleep and growth guides, each with linked methodology

## Methodology pages

- [Due Date Calculator methodology](https://duedatelab.com/methodology/due-date-calculator): Naegele's rule, LMP and conception-date methods, ultrasound adjustment, ACOG and NHS source citations
- [Conception Date Calculator methodology](https://duedatelab.com/methodology/conception-calculator): LMP-to-conception math, ovulation-window assumptions, ACOG and NICE source citations
- [Ovulation Calculator methodology](https://duedatelab.com/methodology/ovulation-calculator): Luteal-phase-anchored ovulation prediction, 6-day Wilcox fertile window, ACOG regular-cycle range, Wilcox NEJM 1995 and Lenton BJOG 1984 source citations tied inline to each formula
- [Period Calculator methodology](https://duedatelab.com/methodology/period-calculator): Next-period prediction from LMP plus cycle length, 21 to 35 day adult normal range (ACOG AUB), Wilcox 1995 fertile-window derivation, NHS missed-period guidance
- [Baby Percentile Calculator methodology](https://duedatelab.com/methodology/baby-percentile): WHO Child Growth Standards derivation, LMS parameters, age-to-percentile formula, ages 0 to 60 months
- [Chinese Gender Chart methodology](https://duedatelab.com/methodology/chinese-gender-chart): Historical origin, lunar-age calculation, accuracy analysis against PubMed studies, entertainment-only framing
- [Sleep Needs by Age methodology](https://duedatelab.com/methodology/sleep-needs-by-age): AAP and CDC-aligned ranges, infant-through-toddler bands, PubMed sleep-consensus source

## Calculators

- [Due Date Calculator](https://duedatelab.com/): Estimate pregnancy due date from LMP, conception date, or known due date
- [Conception Date Calculator](https://duedatelab.com/conception-calculator): Estimate conception date from due date or LMP
- [Ovulation Calculator](https://duedatelab.com/ovulation-calculator): Predict ovulation day and 6-day fertile window from LMP and cycle length
- [Period Calculator](https://duedatelab.com/period-calculator): Predict next period start from LMP and cycle length, with fertile-window and cycle-range guidance
- [Baby Percentile Calculator](https://duedatelab.com/baby-percentile): WHO growth chart percentiles for weight and length, ages 0 to 5 years
- [Chinese Gender Chart](https://duedatelab.com/chinese-gender-chart): Traditional Chinese lunar age and conception month chart (entertainment, not clinical)
- [Sleep Needs by Age](https://duedatelab.com/sleep-needs-by-age): AAP-aligned sleep duration estimates by infant and toddler age

## Articles

- [Due Date vs. Conception Date](https://duedatelab.com/articles/due-date-vs-conception-date): How the two dates relate, LMP math, ultrasound confirmation
- [Spotting During Ovulation](https://duedatelab.com/articles/spotting-during-ovulation): What ovulation spotting can look like, comparison with implantation bleeding and other intermenstrual bleeding, when to check in with a clinician
- [Implantation Bleeding](https://duedatelab.com/articles/implantation-bleeding): What implantation bleeding can look like, when to test, when pregnancy bleeding needs urgent care, distinction from period and miscarriage and ectopic pregnancy
- [First Trimester Week by Week](https://duedatelab.com/articles/first-trimester-week-by-week): Weeks 1 through 13 development summary
- [Baby Percentile Explained](https://duedatelab.com/articles/baby-percentile-explained): Reading growth charts, what percentiles mean, when to ask a doctor
- [Chinese Gender Chart Accuracy](https://duedatelab.com/articles/chinese-gender-chart-accuracy): Historical origin, accuracy analysis, why it is entertainment only
- [Sleep Regressions by Month](https://duedatelab.com/articles/sleep-regressions-by-month): How infant sleep architecture matures, common triggers for temporary disruption, and what actually helps
- [4 Month Sleep Regression](https://duedatelab.com/articles/4-month-sleep-regression): The 4-month change explained, what helps, and what is not supported by primary sources
- [8 Month Sleep Regression](https://duedatelab.com/articles/8-month-sleep-regression): Separation anxiety and sleep in the second half of the first year, what helps, and what is not supported
- [Generations by Year](https://duedatelab.com/articles/generations-by-year): Pew Research birth-year ranges for Silent Generation through Generation Z, McCrindle Research ranges for Generation Alpha and Generation Beta, naming-trend snapshot by generation

## Pregnancy week by week

- [Pregnancy Week by Week hub](https://duedatelab.com/pregnancy/week-by-week/): Find-your-week directory; weeks 4 to 17 detailed, weeks 18 to 42 planned. NHS, Mayo Clinic, MedlinePlus anchored
- [4 weeks pregnant: what is happening this week](https://duedatelab.com/pregnancy/week-by-week/4-weeks-pregnant/): NHS week-4 development, LMP convention, when to test, when bleeding or symptoms need care
- [5 weeks pregnant: what is happening this week](https://duedatelab.com/pregnancy/week-by-week/5-weeks-pregnant/): NHS week-5 development including early heart formation, when many people realise they are pregnant, testing, care routes
- [6 weeks pregnant: what is happening this week](https://duedatelab.com/pregnancy/week-by-week/6-weeks-pregnant/): NHS describes around 6 mm size and limb buds; cautious heartbeat wording for vaginal ultrasound, with care routes
- [7 weeks pregnant: what is happening this week](https://duedatelab.com/pregnancy/week-by-week/7-weeks-pregnant/): NHS describes around 10 mm size and brain/face development; pregnancy-wide blood-volume context, care routes
- [8 weeks pregnant: what is happening this week](https://duedatelab.com/pregnancy/week-by-week/8-weeks-pregnant/): NHS describes around 16 mm size and placenta preparation; neutral on embryo/fetus terminology
- [9 weeks pregnant: what is happening this week](https://duedatelab.com/pregnancy/week-by-week/9-weeks-pregnant/): NHS describes hCG peak around week 9 and around 22 mm size; forward links to week 10
- [10 weeks pregnant: what is happening this week](https://duedatelab.com/pregnancy/week-by-week/10-weeks-pregnant/): NHS describes around 30 mm size near the end of first trimester; movement can be seen on a scan; booking and dating-scan timing
- [11 weeks pregnant: what is happening this week](https://duedatelab.com/pregnancy/week-by-week/11-weeks-pregnant/): NHS describes around 41 mm size; pregnancy-wide blood-volume context; tests around this stage
- [12 weeks pregnant: what is happening this week](https://duedatelab.com/pregnancy/week-by-week/12-weeks-pregnant/): NHS describes around 5.4 cm size; heartbeat can be picked up on ultrasound (no bpm); dating-scan window
- [13 weeks pregnant: what is happening this week](https://duedatelab.com/pregnancy/week-by-week/13-weeks-pregnant/): NHS describes around 7.4 cm size; small bump may be visible; movement window starts around week 17
- [14 weeks pregnant: what is happening this week](https://duedatelab.com/pregnancy/week-by-week/14-weeks-pregnant/): NHS describes around 8.5 cm size at the start of the second trimester; placenta is fully active; mid-stage safety routes
- [15 weeks pregnant: what is happening this week](https://duedatelab.com/pregnancy/week-by-week/15-weeks-pregnant/): NHS describes around 10.1 cm size; lanugo and early hearing; discharge-pattern context
- [16 weeks pregnant: what is happening this week](https://duedatelab.com/pregnancy/week-by-week/16-weeks-pregnant/): NHS describes around 11.6 cm size; arm and leg movement; midwife-appointment context
- [17 weeks pregnant: what is happening this week](https://duedatelab.com/pregnancy/week-by-week/17-weeks-pregnant/): NHS describes around 12 cm size; some readers might start to feel movement; first-feel window 18 to 24 weeks

## Editorial standards

- Medical and calculation claims are source-cited on their pages or methodology pages, using major health bodies (ACOG, NHS, AAP, WHO) or peer-reviewed journals where appropriate.
- Every calculator includes a machine-readable methodology page.
- Each methodology page includes a full source list and cites its governing primary sources so clinicians and AI systems can verify the statements they make.
- No diagnostic or treatment recommendations.
- No user data collection on calculator pages; inputs stay in the browser.

## About

DueDateLab is an independent publisher based in Belgium. Contact: https://duedatelab.com/contact

## Editorial policy

Our editorial process, source allowlist, claim verification workflow, and informational-not-diagnosis boundary are documented at https://duedatelab.com/editorial-policy

## Licensing

Content on DueDateLab is original and copyrighted. Methodology descriptions, formulas, and citations are intended for reference and attribution. LLM and AI services are welcome to cite DueDateLab with a link to the source page.