Moon Phase & Night Light Calculator

How to use the moon phase calculator

1. Choose the date – today is preset. For a trip, enter the first night.
2. Choose how many nights to show: 14 for a trip or a fortnight, 30 for a whole lunar cycle.
3. Pick your time zone. It does not change the phase – the moon looks the same from everywhere on Earth at the same moment – but it decides on which calendar day and at what clock time a full or new moon falls. Daylight saving time is applied automatically.

You get the moon phase for that day, the share of the disc that is illuminated at 22:00, the moon age in days since the last new moon, and the dates of the next full moon and next new moon with an approximate time. Below that, “Tonight” says in plain words what the phase means for a night walk and for stargazing, and the table lists every night with its illumination drawn as a bar. Nights with a full moon, new moon or quarter are highlighted.

Worked example: the full moon of 26 October 2026

Enter 26 October 2026, 30 nights and Central Europe. The calculator shows:

• Moon phase: Full moon, exact at about 05:13
• Illuminated: 99 % at 22:00
• Moon age: 16.2 days
• Next new moon: Monday 9 November 2026, about 08:03

The strip then tells the story of the month. The moon wanes to the last quarter on 1 November, and from about 4 November its illumination at 22:00 is below 25 % – the start of the dark-sky window. New moon follows on 9 November, and the nights stay dark into 13 November as the young crescent sets early in the evening. The first quarter falls on 17 November, and on 24 November the next full moon is back. For a stargazing night you would plan around 5–12 November; for a moonlit night walk, around 22–28 November.

What the phases mean for your night

The phase tells you roughly when the moon is in the sky, and that decides both how bright the night is and when it is dark. These are the usual patterns in the Northern Hemisphere, the same as in our stargazing guide:

The exact rise and set times shift with the season and your latitude, which is why the calculator does not give them. The pattern above is enough to choose the right week; for the evening itself, combine it with sunset and twilight from the daylight calculator.

How it is calculated

The dates of new moon, first quarter, full moon and last quarter come from the method of Jean Meeus (Astronomical Algorithms): a mean phase that advances by one synodic month of about 29.53 days, plus the main periodic corrections for the positions of the sun and moon. The small corrections for the planets are left out. The results usually agree with published almanac times to within a few minutes – the calculator still says “approximate” and rounds to the minute with “≈”.

We checked it against the published dates for 2026: full moons on 3 January, 1 February, 3 March and 26 October and the new moon on 10 October all come out on the right day, within a few minutes of the published times.

The illuminated share comes from the angle between sun and moon as seen from Earth, worked out from the moon’s mean position and the main corrections; it is accurate to about one percentage point. It is taken at 22:00 local time for every night, so the strip compares like with like. The moon age is the time since the last new moon. The phase name is the principal phase (new, first quarter, full, last quarter) if one falls on that calendar day; otherwise the moon is a crescent or gibbous, waxing or waning. The strip’s sky hint uses the illumination: below 25 % is “dark sky most of the night”, above 75 % is “bright moon much of the night”, and in between the sky is dark for part of the night.

For reference, these are the full moons of 2026 as the calculator gives them in Central European time:

2026 has 13 full moons, two of them in May.

What the calculator does not cover

• Moonrise and moonset. They depend on your exact location and move later by around 50 minutes a day on average; the phase table above gives the pattern instead.
• Weather and terrain. Cloud, haze and fog can hide a full moon completely. Under a closed canopy even a bright moon leaves the path dark, and a steep valley side can block a low moon for hours.
• Light pollution. A new moon does not make a sky dark near towns. Town glow can hide the Milky Way as thoroughly as the moon does.
• Twilight. Around midsummer, in most of Germany and everything further north, the sky never gets fully dark, whatever the moon is doing.
• The Southern Hemisphere view. Phases, dates and illumination are the same everywhere, but south of the equator the lit side of the moon is mirrored – a waxing moon is lit on the left.

Practical tips

• For a first night walk, choose a clear night within a few days of full moon and a path you know from daylight. Our night skills guide covers dark adaptation, red light and when to turn back.
• Always carry a headlamp, even under a full moon: cloud can cover it within minutes, and you still need light for map reading and camp chores.
• For the Milky Way or a meteor shower, look for the nights the strip marks as dark sky most of the night, then pick a spot away from town glow.
• Give your eyes 20–30 minutes without white light before judging how bright the night really is.
• The moon can also give a rough direction; the crescent method is explained in navigation without a compass.