Accuracy Policy

The calculators on this site provide estimated dates or timing ranges based on the information entered and on common cycle-based assumptions. They do not guarantee that a specific event will happen on the exact predicted date.

In practical terms, these tools are best used for planning and general understanding, not for certainty.

Accuracy depends heavily on the quality and consistency of the input data. It may be affected by:

• irregular cycles
• short-term cycle variation
• stress or sleep disruption
• illness
• travel or routine changes
• hormonal changes
• medication changes
• uncertain or incomplete tracking history

Period prediction tools are usually most useful when cycle timing is reasonably consistent. If your cycles vary a lot, the output should be treated more like a planning guide than a precise forecast.

That is especially important on pages like the Period Calculator and Next Period Calculator.

Ovulation timing is one of the least certain parts of cycle estimation because it can shift from cycle to cycle. That means fertile window and safe-days calculations are helpful as general timing models, but not guarantees.

In particular, lower-fertility or safe-days estimates should never be read as a promise that pregnancy cannot happen.

This matters most on the Ovulation Calculator, Fertile Window Calculator, and Safe Days Calculator.

A late-period estimate or irregular-cycle estimate can help users compare current timing to past patterns, but it cannot determine the reason for the change. Irregular cycles naturally reduce precision.

That is why the Late Period Calculator and Irregular Period Calculator should be interpreted with extra caution.

Pregnancy timing tools often use the first day of the last menstrual period as a practical starting point. That makes them useful, but still approximate.

Due dates and pregnancy week estimates may later change depending on clinical interpretation, uncertain cycle timing, or scan-based assessment.

The best use of this site is simple:

• use the tools for planning and awareness
• read the guide content that explains the limits
• track your cycle more carefully over time
• avoid treating estimates as fixed medical facts

You may also want to read the Medical Disclaimer for the broader health context.