Period Calculator is a free web-based tool that predicts the next six menstrual periods, ovulation day, and most fertile window. It addresses the need for quick cycle estimates without accounts or data sharing. Users enter the first day of their last period, average cycle length between 21 and 45 days, and average period length between one and ten days to receive instant results.
The calculator follows the standard approach used by many fertility applications and OB-GYNs. It adds the typical cycle length to the last period start date to project future periods, then subtracts 14 days to estimate ovulation because the luteal phase remains relatively stable at about 14 days for most people. The first day of a cycle is defined as the start of full menstrual flow rather than spotting. An optional private tracker allows logging periods on a device-based calendar that learns individual patterns without ever transmitting information to any server.
It is delivered as a mobile-first web application that requires no signup or installation. Results appear immediately in the browser, and all activity stays on the user's device. The service also offers related tools for pregnancy calculations and genetics information through the same site, along with a blog.
No pricing applies because the calculator and tracker are provided at no cost. Nothing is saved to any server.
Period Calculator sits in PulseGate's Lifestyle & Personal category. Accurately predicting upcoming periods, ovulation and fertile days without sharing personal health data. It is built as a consumer product for people who menstruate. A free plan is available. It runs on the web.
Behind Period Calculator is Period Tools, and the product first shipped in 2022. Key capabilities include Period Prediction, Ovulation Calculator, and Fertile Window.
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