Does the due date calculator upload my data?

No. The core calculation runs in this browser. Permission-based device streams stay local unless you explicitly download a result.

How accurate is the result?

Accuracy depends on the inputs and hardware. The page labels estimates and calibration limits; use an approved instrument or official source for safety, medical, financial or travel decisions.

Can I use it offline?

Yes. The calculation and UI do not require an external API or account. Browser permissions and device sensors may still be unavailable on some platforms.

Pregnancy Due Date Calculator — Free Online Tool

Why Sleep Calculators Count in 90-Minute Cycles, Not Hours

The math behind working backward from a wake-up time (or forward from a bedtime) in whole 90-minute sleep cycles, and why waking mid-cycle is what actually causes grogginess.