What is the moon phase tonight?

Enter tonight's date and the page names it from the eight standard phases and gives the percentage of the disc that is lit. A phase lasts about three and a half days, so the answer is the same for a few nights running; what changes visibly from night to night is the illumination, which moves by roughly 8 percentage points a day in the middle of the cycle and much faster near the quarters. The moon phase tonight is best read together with the moon age, because two nights with the same percentage can be three weeks apart.

How is the moon illumination percentage worked out?

From the sun–moon elongation, which is the angular distance between the two as seen from Earth. Illumination is (1 − cos elongation) / 2, so 0° gives 0%, 90° gives 50%, 180° gives 100% and 270° gives 50% again. Nothing about the moon's distance or the observer's location enters into it, which is why the same percentage is correct for everyone on Earth at a given instant.

What does moon age mean?

Moon age is the number of days since the last new moon, so it always starts at 0 and runs to about 29.5 before resetting. It is 0–1 day in the day or two after a new moon, around 7 at first quarter, 14 to 15 at full moon and 22 at last quarter. Astronomers and almanacs use the age rather than the phase name when they need a number, and the two always agree here because both come from the same elongation.

How do I find the next new moon date or full moon date?

Both are printed next to the illumination, and both are strictly after the day you entered — the page reports the new moon you are waiting for, never the one already past. Around half of the entries will show a new moon that is less than a full cycle away, and the gap between the two printed dates is never more than about 15 days. For a longer run of dates, step through the months rather than assuming a 29.5-day rhythm: the true spacing varies from about 29.2 to 29.9 days.

Does the moon phase calculator use my time zone?

No, and deliberately so. The moon phase calculator reads the disc at 12:00 UTC on the date you enter, so the same date gives the same answer wherever you are, and the page needs no clock of yours to work. The one thing that follows from this is that a phase which turns over late in the UTC day is reported in its earlier state; the offsets involved are at most 14 hours, which is well under the roughly three and a half days a phase lasts.

Moon Phase Calculator

Result

10.2%Waning crescent

Illumination

Moon age: 26.4 days
Sun–moon elongation: 322.7 °
Last new moon: December 20, 2025
Next new moon: January 18, 2026
Next full moon: February 1, 2026

The moon phase calculator answers the question people actually ask — what does the moon look like tonight — and then the two questions underneath it: how much of it is lit, and how far it has come since the last new moon. Enter any date and the page reports the illumination as a percentage, the moon age in days, the elongation between sun and moon, and the phase name out of the eight standard ones. It also gives the dates of the surrounding new moon and the next full moon, so a month of stargazing, photography or fasting can be laid out around the dark nights.

The eight phases, the illumination each one covers, and when it is up

Phase	Illumination	When it is visible
New moon	0.0 – 3.8%	The moon sits between Earth and the sun, so the lit half faces away and the disc is dark. It rises and sets with the sun and is invisible except during a solar eclipse. The percentage here is the thinnest sliver before or after the exact instant.
Waxing crescent	3.8 – 30.9%	A growing crescent, lit on its right-hand side from the northern hemisphere, visible low in the west after sunset and setting in the evening. Because the range overlaps the waning crescent's exactly, the percentage alone cannot tell you which of the two you are looking at — that is what the elongation decides.
First quarter	30.9 – 69.1%	Half the disc is lit, and it is the right-hand half as seen from the northern hemisphere. It stands highest around sunset and sets around midnight. The name says a quarter even though half the disc is bright: it marks a quarter of the way through the cycle, not a quarter of the visible area.
Waxing gibbous	69.1 – 96.2%	More than half lit and still growing, on the way to full. It is up in the afternoon and dominates the evening sky. The range is identical to the waning gibbous range, so a percentage in the eighties tells you how bright it is but not whether the moon is filling in or emptying out.
Full moon	96.2 – 100%	The disc is fully lit, rising around sunset and staying up all night. It is only exactly 100% at the instant of opposition — a day either side reads 99% and looks the same to the eye. Lunar eclipses only ever happen here.
Waning gibbous	96.2 – 69.1%	Past full and shrinking. It rises after sunset and is still in the sky in the morning, so it is the phase most often mistaken for the full moon. The numbers run backwards through the same range as the waxing gibbous, and only the elongation separates the two.
Last quarter	69.1 – 30.9%	Half the disc is lit again, this time the left-hand half from the northern hemisphere. It rises around midnight and stands highest at dawn, so it belongs to the second half of the night. Three quarters of the cycle are behind it and about a week is left before the next new moon.
Waning crescent	30.9 – 3.8%	The last thinning crescent, visible low in the east before sunrise and gone by mid-morning. Its illumination range covers the same span as the waxing crescent, so the percentage cannot name it; the elongation, which is past 270° here, is what does. A few days later the cycle closes at the new moon.

The middle column is a description of each sector's width, not the rule that decides the phase. Waxing and waning crescent share one range, as do the two gibbous phases, because the percentage cannot tell a growing moon from a shrinking one — only the elongation, which runs from 0° to 360° once per cycle, carries that direction. Read the middle column as a rough brightness guide and the first column as the answer.

Formula

elongation = moon longitude − sun longitude, taken in 0–360°; illumination = (1 − cos elongation) / 2; age = days since the last new moon; phase name = which 45° sector the elongation falls in

date: The calendar day to look up, written as YYYY-MM-DD. The phase is sampled at 12:00 UTC on that day, not at your local midnight
illumination: The share of the disc that is lit, as a percentage. It runs 0% at new moon to 100% at full moon and back, and it is the headline number
age: The moon age: days elapsed since the last new moon. It starts near 0 right after a new moon and climbs to about 29.5 before the next one
elongation: The sun–moon elongation in degrees, from 0° at new moon through 90° at first quarter and 180° at full moon to 270° at last quarter. It sets the phase name
lastNewMoon: The date of the most recent new moon, on or before the day entered
nextNewMoon: The date of the next new moon after the day entered
nextFullMoon: The date of the next full moon after the day entered

Use it to plan around moonlight rather than to plan around a date: the week either side of a full moon washes out faint stars and the Milky Way, while the days around a new moon are the dark ones for astrophotography and for spotting meteor showers. It is also the quick check behind a hundred other decisions — whether the moon will be up and bright for an evening walk, how much light a night-shift or a night-time survey has to work with, and which night a monthly or lunar-calendar event actually falls on. For the moon's position in the sky, its rising and setting times, or tides, a different tool is needed: this page describes the disc, not where to look for it.

Worked examples

15 January 2026 — a waning crescent
1. The last new moon before this date was on 20 December 2025, so the moon age is the distance from that instant to noon on 15 January: 26.4 days
2. The sun–moon elongation works out at 322.7°, which lands in the sector that runs from 315° to 337.5° — the waning crescent
3. Illumination follows from the elongation alone: (1 − cos 322.7°) / 2 = 0.102, so 10.2% of the disc is lit
4. The next new moon is three days later, on 18 January 2026, and the next full moon after that is on 1 February 2026
5. A moon age of 26.4 days sits in the last quarter of the cycle, which is why the crescent is thinning rather than growing
This is the kind of night the page is most useful for: a thin crescent, a dark sky, and only three days left before the moon disappears entirely. It is also the case that shows why the illumination percentage cannot name the phase — 10.2% lit is a waning crescent here, and the same 10.2% three weeks earlier would have been a waxing one.
3 March 2026 — the full moon itself
1. The full moon falls at 11:38 UTC on this date, and the page samples noon, so the elongation comes out at 180.2° — just past exact opposition
2. An elongation of 180.2° gives (1 − cos 180.2°) / 2 = 0.99999, which rounds to 100.0% at one decimal place
3. The moon age is 14.0 days, the midpoint of the roughly 29.5-day cycle that started with the new moon on 17 February 2026
4. The next new moon is on 19 March 2026 and the next full moon on 2 April 2026, so this page reports the full moon you are standing in and the one after it, not the same one twice
The one date in the month where the headline reads exactly 100.0%. It is worth knowing that the disc is only a fraction of a degree from perfect opposition here: on a night a day either side, the number is 99.5% or so and looks identical to the eye. That gap is why the phase name is graded on the 45° sectors rather than on the percentage.
8 April 2024 — a total solar eclipse, still a new moon
1. The new moon of 8 April 2024 happens at 18:21 UTC, and this page reads the disc at noon — about six hours before the exact instant
2. Six hours short of a new moon leaves an elongation of 356.5°, so the illumination is not 0% but 0.1%
3. The moon age is 29.1 days, counted from the previous new moon on 10 March 2024, which is as old as the cycle gets
4. The next new moon is the one this date is hours away from — still 8 April 2024 — and it is the new moon that carried the total solar eclipse across North America that afternoon
A solar eclipse only ever happens at a new moon, and this is the useful reminder that a new moon is an instant rather than a day. A tool that treated the whole date as 'new moon' would report 0.0% and a fresh 0.0-day age here, and would be wrong about both by a wide margin. The page itself reports the eclipse day as the oldest moon of its cycle.

Limitations

The phase is sampled at 12:00 UTC on the date you enter, not at your local midnight, so a transition that happens during your night is reported as it stood at noon. The page describes the disc and nothing else: it will not tell you when the moon rises or sets, how high it climbs, whether it is above the horizon right now, or how big the tides will be, and it does not predict eclipses. Accuracy on the new moon and full moon instants is within about half an hour against NASA's published tables for 2001–2025, which is the span this was checked over; outside it the series is extrapolated and drifts slowly. No lunar calendar date is shown.

Frequently asked questions

What is the moon phase tonight?: Enter tonight's date and the page names it from the eight standard phases and gives the percentage of the disc that is lit. A phase lasts about three and a half days, so the answer is the same for a few nights running; what changes visibly from night to night is the illumination, which moves by roughly 8 percentage points a day in the middle of the cycle and much faster near the quarters. The moon phase tonight is best read together with the moon age, because two nights with the same percentage can be three weeks apart.
How is the moon illumination percentage worked out?: From the sun–moon elongation, which is the angular distance between the two as seen from Earth. Illumination is (1 − cos elongation) / 2, so 0° gives 0%, 90° gives 50%, 180° gives 100% and 270° gives 50% again. Nothing about the moon's distance or the observer's location enters into it, which is why the same percentage is correct for everyone on Earth at a given instant.
What does moon age mean?: Moon age is the number of days since the last new moon, so it always starts at 0 and runs to about 29.5 before resetting. It is 0–1 day in the day or two after a new moon, around 7 at first quarter, 14 to 15 at full moon and 22 at last quarter. Astronomers and almanacs use the age rather than the phase name when they need a number, and the two always agree here because both come from the same elongation.
How do I find the next new moon date or full moon date?: Both are printed next to the illumination, and both are strictly after the day you entered — the page reports the new moon you are waiting for, never the one already past. Around half of the entries will show a new moon that is less than a full cycle away, and the gap between the two printed dates is never more than about 15 days. For a longer run of dates, step through the months rather than assuming a 29.5-day rhythm: the true spacing varies from about 29.2 to 29.9 days.
Does the moon phase calculator use my time zone?: No, and deliberately so. The moon phase calculator reads the disc at 12:00 UTC on the date you enter, so the same date gives the same answer wherever you are, and the page needs no clock of yours to work. The one thing that follows from this is that a phase which turns over late in the UTC day is reported in its earlier state; the offsets involved are at most 14 hours, which is well under the roughly three and a half days a phase lasts.

References

Phases of the Moon, 2001 to 2025 (Universal Time) — NASA Goddard Space Flight Center, Eclipse Web Site
Moon Phases — NASA Science

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