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Health & FitnessGenerated accuracy model review: 2026-05-06
Pregnancy Calculator accuracy and testing
This page documents how Calwarden builds trust for this calculator: source notes, regression-style default tests, limitations, assumptions, unit handling, rounding, and visible change history.
Formula source
- The calculator uses **Naegele's Rule**: LMP + 280 days (40 weeks). It adjusts for cycle length: if your cycle is longer than 28 days, your due date is pushed later; if shorter, it's earlier.
Test cases
Default input regression check
Generated from the checked-in default inputs and calculate function.
Inputs
- First Day of Last Period: 2026-09-24
- Average Cycle Length: 28 days
Expected outputs
- Estimated Due Date: Wednesday, June 30, 2027
- Approx. Conception: October 7, 2026
- Current Status: 0 weeks, 1 days
Known limitations
- This page documents the checked-in calculator logic and does not certify results for every real-world edge case.
- Use the result as a planning estimate unless the calculator page states a stricter purpose.
Assumptions
- The estimate uses Naegele's Rule and assumes the pregnancy is dated from the first day of the last period.
- Cycle-length adjustment assumes ovulation shifts roughly with the difference from a 28-day cycle.
- Ultrasound dating may change the estimate, especially with irregular cycles or uncertain LMP dates.
Unit handling
- First Day of Last Period accepts calendar dates.
- Average Cycle Length accepts values in days.
Rounding rules
- Number displays use up to 2 decimal places in the calculator UI.
Version history
1.0.0 - 2026-05-06
Generated accuracy and testing page from the current pregnancy-due-date-calculator calculator definition.
Change log
2026-05-06
Published default regression test documentation and metadata fallbacks for Pregnancy Calculator.
Calculator transparency
Accuracy pages are generated from checked-in calculator definitions and can be upgraded with curated review metadata over time.