Period Calculator

Use it for simple educational checks, trend tracking, or planning tasks like these: Estimate the next period start date. Estimate expected period end date. It can help you understand a number, but it cannot explain your whole health situation.

Enter the body, activity, date, or lab values exactly in the units shown on the page. Height, weight, age, sex, time, and activity level can change health estimates a lot, so treat each label like a rule instead of a suggestion. If you are unsure which option fits, choose the closest honest match and read the result as a rough estimate.

In plain language: The calculator adds cycle length to the first day of the last period until it finds the next expected period start date. Read the result together with the notes on the page, because health and fitness numbers often need personal context.

Use the result as a learning number, not a final answer about your body or health. The supporting lines can show categories, ranges, calories, dates, or targets, but those numbers still need context like age, medical history, pregnancy status, training level, and advice from a qualified professional.

No. This page provides an educational estimate only. Talk with a qualified health professional before making medical, pregnancy, nutrition, medication, or safety decisions. Use the calculator as a learning tool, then ask a qualified professional about decisions that affect care, pregnancy, medication, nutrition, or safety.

Check the units, date, and personal details before reading the answer. For example, pounds and kilograms, inches and centimeters, or a wrong activity level can change the result quickly. If the number feels surprising, rerun it slowly and compare it with the examples.

No. The calculator runs in your browser tab. Recent answers stay only on the page while you use it, and they are not sent to a server.