Lunar Month Calculator

About the Lunar Month Calculator

The Lunar Month Calculator is a free moon tool. Count the number of lunar months between two dates, like counting moons. It runs on the same NASA-grade math we use across the whole site, so every answer matches the real moon in the sky to within a few minutes. This lunar month tool is built to make the lunar cycle easy to follow for anyone, with no astronomy background needed.

Using the Lunar Month Calculator is simple. Pick any date with the date picker above (or leave it on today) and the widget updates instantly — no button to press, no page to reload. The tool works for any day in the past or the future, so you can check what the moon looked like on your birthday, what it will look like next year, or what it is doing right now. The synodic month data is computed right inside your browser, which means it is fast and private.

Every moon tool on this site is free forever, with no signup and no app to install. We built the Lunar Month Calculator because we wanted lunar month to be as easy as glancing at a clock. If you find it useful, the related tools and calculators below cover every other question you might have about moon cycle length.

• Free forever — no signup, no app to install.
• Works for any date — past, present, or future.
• Same NASA-grade moon math used across the whole site.
• Updated in real time, right inside your browser.