Moon Phase Calculator

Check today or another date using a lightweight astronomical approximation that runs locally in your browser.

Date

Time basis

—Phase

—Lunar age

—Illuminated

—Cycle progress

🌙Approximate lunar phase

Uses a synodic-month approximation referenced to a known new moon. It is useful for everyday phase checks but is not an ephemeris for precision astronomical work.

How to use this Moon Phase Calculator

Estimate the Moon phase, lunar age, and illuminated fraction for a selected date. Enter your values above and the result is calculated directly in your browser. No account is required.

Fast answer, clear inputs

This tool is built around one job: give the answer quickly without forcing a signup or hiding the result. Related tools are linked nearby when the next calculation or conversion is useful.