Moon Phase Calculator
The Moon phase on a given date tells you how much of the Moon was lit and where it was in its cycle — from new moon to full moon and back. Great for birthdays and any date.
Using the Moon Phase calculator
Pick a date
Choose any date — your birthday, today, or any day you like.
We compute the phase
The Sun–Moon angle for that date gives the phase and illumination.
See the result
You get the phase name, illumination percentage and Moon age in days.
About the Moon Phase calculator
The lunar cycle has guided calendars, festivals and farming for millennia. Knowing the Moon phase on a date connects that date to the natural rhythm of the sky.
Frequently asked questions
What are the Moon phases?
The Moon cycles through new moon, waxing crescent, first quarter, waxing gibbous, full moon, waning gibbous, last quarter and waning crescent over about 29.5 days.
How accurate is this?
It uses a well-known astronomical approximation, accurate to within a few hours of illumination — plenty for finding the phase on any date.
What is a birthday moon phase?
It's simply the Moon phase on the day you were born — a fun detail some people like to know about themselves.
Go deeper than a free tool
A personalized AstroHood report reads your whole birth chart and numbers together — for money, marriage and life — as a beautifully designed premium PDF.
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