Moon Phase Calculator
See the current moon phase, illumination percentage, and moon age, plus the next new moon, full moon, and upcoming phase dates.
Calculated in your browser as an astronomical approximation, accurate to within a few hours. Every phase time is shown in your own local time zone.
Calculating the current moon phase...
How to check the current moon phase
Check today automatically
The tool opens already set to right now, showing the current moon phase, illumination, and age as soon as the page loads.
Pick a different date
Choose any date to see the moon phase on that day instead, useful for planning ahead or looking back.
Add a time for more precision
Set a time of day to get the phase for that exact moment rather than midnight on the chosen date.
Copy the summary
Click Copy summary to copy the phase name, illumination, and moon age as a short line of text.
Why use this tool
Live by default
Opens already showing the moon phase for right now, with no date to pick first.
Illumination and moon age
Shows the percentage of the moon's disc that is lit and how many days it has been since the last new moon.
Next and previous key phases
Cards show the next new moon, next full moon, previous new moon, and the current lunation number.
Eight phases ahead
Lists the next eight principal phases in order, each with its date, so you can plan around a full moon or a new moon.
Private by design
Every calculation runs in your browser against your device clock, and nothing is uploaded.
About this tool
This tool works out the current moon phase for any date and time: the phase name, from new moon through to waning crescent, the percentage of the moon's disc that is lit, and the moon's age in days since the last new moon. It opens already set to the current moment, so the first thing you see is the phase for right now rather than an empty form waiting for input.
Change the date to look at any other day, past or future, and add a time of day for a more precise reading, since the phase shifts gradually through each day rather than jumping at midnight. Alongside the headline phase, four cards show the next new moon, the next full moon, the previous new moon, and the current lunation number, a running count of full lunar cycles from a fixed reference new moon. A further list sets out the next eight principal phases, new moon, first quarter, full moon, and last quarter, in order with their dates, useful for planning a stargazing night, a photography shoot, or anything else timed around moonlight.
The result is an astronomical approximation based on the average length of a lunar month, accurate to within a few hours rather than to the minute, and every phase time is shown in your own local time zone. Everything runs in your browser with nothing uploaded. To count the days until a specific date instead, use the days until date calculator, to measure the span between two fixed dates use the date difference calculator, and to check what day of the week a date falls on use the day of the week calculator.
Frequently asked questions
- How accurate is the moon phase calculation?
- The result uses the average length of a lunar month and is accurate to within a few hours. It will not exactly match specialized data used for eclipse prediction, but it is well within range for everyday planning.
- What time zone are the phase dates shown in?
- All dates and times, including the upcoming phases list and the next and previous new and full moon cards, are shown in your device's own local time zone.
- What is the lunation number?
- It is a running count of full lunar cycles measured from a fixed reference new moon, increasing by one every time a new moon occurs. It is a way of labelling which lunar month you are currently in.
- What does moon age mean?
- Moon age is the number of days that have passed since the most recent new moon. It runs from 0 at a new moon up to just under 29.5 days before resetting at the next new moon.
- Is my chosen date and time kept private?
- Yes. The whole calculation runs in your browser against your device clock. Nothing you enter is uploaded, stored, or logged.
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