Check the moon phase for any date — illumination, moon age, distance, moonrise & moonset. Find your birthday moon, compare couple moons (just for fun), browse the lunar calendar, or download a moon-phase wallpaper. Free, no signup, 100% client-side.
How accurate is this? Phase and illumination are computed from the 29.530588853-day synodic month and verified against US Naval Observatory data (e.g. the Oct 7, 2025 Harvest Moon reproduces at 99.99% illumination). Moonrise/moonset times are approximate (±15 min). Everything runs locally in your browser — your dates never leave your device.
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Illumination
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Moon age
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Distance
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Next full moon
Next new moon: —
What moon were you born under?
Enter your date of birth to see the exact moon phase on that day — the viral "birthday moon". For the most precise result including your birth time, use the Phase Calculator tab with a date & time instead.
Couple moon-phase comparison
Just for fun. Matching two birth moons is a TikTok trend — it is entertainment, not astrology and not science. The moon does not decide how two people get along. The score below measures only how visually similar the two moons are.
See how your two moons line up side by side — a visual moon-phase love match, for fun only.
Lunar calendar
Visual chart of every day's moon for any month, January through December.
Moonrise & moonset
When is the moon rising tonight? Approximate moonrise and moonset times (typically within ~15 min) for any location worldwide, computed locally from your coordinates. Nothing is sent anywhere.
Moon-phase wallpaper
Render a 1080×1920 phone wallpaper picture of any date's moon and download it as PNG.
How moon phases are calculated
The moon orbits Earth every 29.530588853 days (the synodic month — new moon to new moon). Measuring from a known new moon (January 6, 2000, 18:14 UTC), the moon's age on any date gives the phase angle, and the illuminated fraction is:
illumination = (1 − cos(phase angle)) / 2
The phase angle (in degrees, 0° at new moon through 360°) also tells you the moon's elongation from the sun — the same angle eclipse predictors use.
This calculator implements that math directly in your browser and has been verified against US Naval Observatory data: it reproduces the October 7, 2025 Harvest Moon at 99.99% illumination and the solar-eclipse new moons of September 2025 and August 2026 below 1%. Moon distance uses a truncated lunar-orbit model (accurate to a few hundred km); moonrise/moonset uses the same orbit model with standard rise/set geometry and is approximate to about ±15 minutes.
Use the formula in Excel or Python
Excel / Google Sheets — with a date in A1, moon age in days is =MOD(A1-36530.76, 29.530588853) (36530.76 is the serial for the Jan 6, 2000 new moon). Illumination % is =(1-COS(2*PI()*B1/29.530588853))/2*100 where B1 holds the age.
Python — age = (jd - 2451550.26) % 29.530588853; illum = (1 - math.cos(2*math.pi*age/29.530588853)) / 2, where jd is the Julian Day. No app download is needed for any of this — the calculator above runs in any browser.
The 8 moon phases
How many moon phases are there? Eight named phases make up one full cycle:
Phase
Moon age
Illumination
What you see
New Moon
0 d
0%
Dark disc; moon between Earth and Sun
Waxing Crescent
~3.7 d
~25%
Right-side sliver growing (Northern Hemisphere)
First Quarter
~7.4 d
50%
Right half lit
Waxing Gibbous
~11.1 d
~75%
More than half lit, growing
Full Moon
~14.8 d
100%
Whole disc lit; rises at sunset
Waning Gibbous
~18.4 d
~75%
More than half lit, shrinking
Last Quarter
~22.1 d
50%
Left half lit
Waning Crescent
~25.8 d
~25%
Left-side sliver shrinking
In the Southern Hemisphere the lit side appears mirrored — toggle "Southern Hemisphere view" in the calculator.
How this compares
Tool
Phase + illumination
Birthday mode
Couple comparison
Wallpaper
Moonrise / moonset
Lunar calendar
This calculator (nrtechstudio.com)
Yes
Yes
Yes (fun-only)
Yes (PNG)
Yes (approx.)
Yes
complete.tools
Yes
No
No
No
Yes
Yes
mylunarsoulmate.com
Basic
Yes
Yes (astrology)
No
No
No
timeanddate.com
Yes
No
No
No
Yes
Yes
Comparison based on the public pages of each tool as of October 2026. Feature sets change; unlike the astrology-flavored soulmate sites, this page treats compatibility as entertainment only and shows its astronomy method openly.
Frequently asked questions
What is my moon phase?
Enter any date and time in the calculator above and you will see the exact moon phase, illumination percentage, and moon age for that moment. Your birth moon phase is the phase on your date of birth — use the Birthday Moon tab.
How is the moon phase calculated?
This calculator uses the mean synodic month of 29.530588853 days measured from a known new moon (January 6, 2000, 18:14 UTC). The moon's age gives the phase angle, and illumination is (1 − cos(angle)) / 2. The method is verified against US Naval Observatory data: it reproduces the October 7, 2025 Harvest Moon at 99.99% illumination and the 2026 solar-eclipse new moons below 1%.
What moon phase was I born under?
Use the Birthday Moon tab and enter your date of birth. The tool shows the phase name, illumination, and a visualization of the moon as it appeared that day. About 1 in 8 people are born under a full moon.
What are the 8 phases of the moon?
New Moon, Waxing Crescent, First Quarter, Waxing Gibbous, Full Moon, Waning Gibbous, Last Quarter, and Waning Crescent. "Waxing" means the lit part is growing toward full; "waning" means it is shrinking toward new.
How accurate is this moon phase calculator?
Phase fraction and illumination are accurate to well under 1% for any date. The 8-phase name boundaries are approximate to about ±0.4 day because the real lunar orbit is slightly irregular. Moonrise and moonset times use a simplified lunar-position model and are approximate, typically within about 15 minutes — fine for planning, not for navigation.
What does moon illumination percentage mean?
The percentage of the moon's visible disc that is sunlit as seen from Earth: 0% at new moon, 50% at the quarters, 100% at full moon. It is computed as (1 − cos(phase angle)) / 2.
What is the age of the moon?
The moon's age is the number of days since the last new moon, from 0 to about 29.53. A 7.4-day-old moon is near first quarter; a 14.8-day-old moon is full.
When is the next full moon?
The calculator above shows the next full moon date automatically for any date you enter, along with a countdown in days. The Moon Calendar tab also lists every day's phase for the whole month.
When is the next new moon?
Enter any date in the calculator and the next new moon date and countdown appear next to the next full moon. New moons are when the moon is between Earth and the Sun and its dark side faces us.
Does the moon phase affect my personality?
There is no scientific evidence that the moon phase at your birth affects your personality. Large studies have found no link between lunar phases and human behavior. Treat birth-moon meanings as entertainment, not fact.
Can the moon phase predict a baby's gender?
No. There is no scientific basis for predicting a baby's gender or fertility from the moon phase, despite old folklore. A baby's sex is determined at conception.
What is a moon phase soulmate or compatibility calculator?
It is a viral TikTok trend — sometimes called a twin-flame or synastry calculator — where two people's birth moons are compared visually. It is entertainment only: there is no scientific basis for moon-phase compatibility. Our Couple Moons tab says so openly and scores only how similar the two moons look.
Why does the moon look upside down in Australia?
In the Southern Hemisphere the moon appears rotated about 180° compared to Northern Hemisphere views, because observers are effectively "upside down" relative to each other. Use the Southern Hemisphere toggle in the calculator to see the mirrored view.
What is the difference between a moon phase and a zodiac sign?
They are unrelated. Moon phase is an astronomical fact — how much of the moon is sunlit. Zodiac signs are astrological categories based on the Sun's apparent position. This tool computes only the astronomy.
How are moonrise and moonset times calculated?
From a simplified model of the moon's orbit (low-precision lunar theory) plus the standard rise/set geometry for your latitude and longitude, using +0.125° altitude for the moon's upper limb. Results are approximate, typically within about 15 minutes of authoritative almanacs.
What is a supermoon?
A full moon that occurs near the moon's closest approach to Earth (perigee, about 356,400 km). It can look up to about 14% larger and 30% brighter than a full moon at apogee. The calculator shows the moon's current distance so you can spot them.
How long is a complete lunar cycle?
The synodic month — the full lunar cycle period from new moon to new moon — averages 29.530588853 days (about 29 days, 12 hours, 44 minutes). That is why most calendar months contain exactly one full moon, and occasionally two (the second is called a blue moon).
Can I check the moon phase for a date in the past or future?
Yes — enter any date, past or future. The calculation is pure math done locally in your browser, so historical dates (for example a birthday decades ago) work just as well as next year's full moons.
How do I set the moonphase complication on my watch?
Look up today's moon age with the calculator above, then advance your watch's moon disc to the matching phase using its pusher or crown position. Most moonphase watches assume a 29.5-day cycle, so they drift about a day every 2–3 years — re-sync at a known full moon.
What is the Hawaiian moon calendar?
The traditional Hawaiian lunar calendar (Kaulana Mahina) gives a name to each night of the month, from Hilo (first crescent) through Kulu (full). It tracks the same astronomical cycle this calculator computes — the phase, age, and illumination shown above underlie those traditional names.
Privacy: everything runs locally in your browser — your birth dates and location never leave your device. No account, no tracking of inputs.
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