Health & FitnessGenerated accuracy model review: 2026-05-06

Ovulation & Period 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

For a regular cycle, ovulation usually happens roughly 14 days *before* your next period starts. * **Next Period** = Last Period + Cycle Length * **Ovulation** = Next Period - 14 Days * **Fertile Window** = 5 days before Ovulation + Ovulation Day.

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
Cycle Length: 28 days

Expected outputs

Est. Ovulation Date: Oct 7
Fertile Window: Oct 2 - Oct 7
Next Period Starts: Oct 21

Known limitations

Assumes a regular cycle and a standard 14-day luteal phase. Stress, illness, and hormonal imbalances can shift ovulation.

Assumptions

The estimate assumes a fairly regular cycle and a typical luteal phase length.
Ovulation timing is inferred from cycle dates rather than confirmed by temperature, ultrasound, or hormone testing.
Stress, illness, postpartum changes, and hormonal conditions can shift real ovulation timing.

Unit handling

First Day of Last Period accepts calendar dates.
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 ovulation-calculator calculator definition.

Change log

2026-05-06

Published default regression test documentation and metadata fallbacks for Ovulation & Period.

Calculator transparency

Accuracy pages are generated from checked-in calculator definitions and can be upgraded with curated review metadata over time.

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