Pick any date, see the moon phase, illumination percentage and moon age, plus this month's principal phases, all in your browser
- Runs locally
- Category Calculator
- Best for Getting a realistic range before a purchase, plan, workout, or schedule decision.
- Full Moon2026-05-01
- Last Quarter2026-05-09
- New Moon2026-05-16
- First Quarter2026-05-24
- Full Moon2026-05-31
Astronomical estimate from the 29.53-day synodic month — accurate to about ±1 day. For an exact rise/set time use a local almanac.
What this tool does
A free moon phase calculator that tells you what the Moon looks like on any date past or future. Enter a day and it returns one of the eight classical phases (new moon, waxing crescent, first quarter, waxing gibbous, full moon, waning gibbous, last quarter, waning crescent), the illuminated fraction of the disc as a percentage, and the moon age in days since the most recent new moon. A drawn moon disc and a phase emoji give you the picture at a glance, and the tool also lists the four principal phase dates that fall inside that calendar month so you can plan around the next full moon or new moon. The math is a synodic-month model: the Moon repeats its phases every 29.53059 days, so we count the days elapsed since a known new moon (2000-01-06 18:14 UTC) and take the remainder. That makes it an astronomical estimate accurate to roughly one day, perfect for stargazing, photography planning, fishing and gardening almanacs, or just knowing whether tonight is a full moon. Everything runs client-side, the date lives in a shareable URL, and nothing is uploaded.
Tool details
- Input
- Files + Numbers
- The page exposes text boxes, numeric controls, file pickers, or structured inputs depending on the tool.
- Output
- Live result + Copy + Preview
- The result area focuses on usable output, with copy, download, or preview actions when supported.
- Privacy
- Browser-side processing
- The main tool logic does not call an external API, so inputs normally stay in the current tab.
- Save / share
- Shareable URL state
- Key settings are encoded in the URL so another person can reopen the same setup.
- Performance budget
- Initial JS <= 10 KB
- No WASM budget is declared, keeping the tool quick to open on mobile.
- Best fit
- Calculator · Student
- Category and role tags drive related tools, internal links, and quick fit checks.
How to use
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1. Input
Paste or drop your content into the tool panel.
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2. Process
Click the button. All processing is local in your browser.
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3. Copy / Download
Copy the result or download to disk in one click.
How Moon Phase Calculator fits into your work
Use it for fast estimates, comparisons, and planning numbers before you make the final call.
Calculation jobs
- Getting a realistic range before a purchase, plan, workout, or schedule decision.
- Comparing scenarios by changing one input at a time.
- Turning rough assumptions into a number you can discuss.
Calculation checks
- Double-check units, dates, rates, and rounding assumptions.
- Treat health, finance, tax, and legal outputs as planning aids, not professional advice.
- Save the inputs that produced an important result so you can reproduce it later.
Good next steps
These links move the current task into a more complete workflow.
- 1 Age Calculator Calculate your exact age — years, months, days, hours. Compare two dates or count to a future date. Open
- 2 Lunar Calendar Converter (Chinese Nongli) Gregorian ⇄ Chinese Lunar (Nongli) calendar — bi-directional, accurate 1900-2100. Open
- 3 Western Zodiac Calculator (Sun Sign) Western zodiac calculator — your sign, element, ruling planet, compatibility, daily traits. Open
Real-world use cases
Plan a moon photography or stargazing night
A new moon means a dark sky, ideal for the Milky Way and faint deep-sky objects, while a full moon washes them out but lights up a landscape shot. Set the date you are scouting, read the illumination percentage, and pick the night that matches the picture you want. The principal phases list also tells you when the next new moon falls so you can book the darkest weekend.
Caption a post or video with the right phase
A content creator filming a night scene wants the caption to say the actual phase, not a guess. Type the shoot date, copy the phase name and illumination, and paste it straight into the description. The emoji disc gives you a thumbnail-ready shape, and the shareable link lets an editor open the exact same date to double-check.
Check tonight's moon for fishing or gardening
Many anglers and gardeners follow lunar almanacs that key tasks to the phase. Open the tool on today, see whether the Moon is waxing or waning and how full it is, and line up your planting or trip with the tradition you follow. No login, no almanac subscription, just the phase for the day in front of you.
Settle a "was it a full moon that night" question
Trying to remember whether a memorable evening, a wedding or an incident happened under a full moon? Punch in the past date and the tool reconstructs the phase and illumination for that exact day. Because it is a deterministic calculation, you get the same answer every time and can paste the link as evidence.
Common pitfalls
Reading a quarter moon as 25 percent lit. First and last quarter are about 50 percent illuminated. The word quarter means one quarter of the way through the cycle, not a quarter of the disc, so the tool correctly shows roughly 50 percent at those phases.
Expecting the calculated date to match an almanac to the hour. This is a synodic-month estimate with about one day of slack, because the real lunar cycle speeds up and slows down. Use it for planning, not for precise eclipse or moonrise timing.
Confusing waxing and waning. Waxing means the lit fraction is growing toward full, waning means it is shrinking toward new. A 60 percent disc could be either, so check the direction label the tool shows next to the phase name.
Privacy
The phase, illumination and moon-age math is plain JavaScript that runs entirely in your browser tab. No date you enter is sent anywhere and nothing is logged. The one thing to know: the date is encoded in the page URL so the link is shareable, which means a link you paste into chat will record that date in the recipient server's access log. If a date is sensitive, use the copy button to grab the text result instead of sharing the URL.
FAQ
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