Moon Phase Calculator
See the lunar phase name and how much of the moon is illuminated on a chosen date.
By Aryan Khan, Founder & Editor · Updated October 2026
For example, for 22 October 2026 the dashboard reads: waxing gibbous, about 86% illuminated, age about 11.1 days, full moon roughly three days ahead — one date, the whole lunar story.
How to use Moon Phase Calculator
One date in — phase, light and the road ahead out:
The Moon Phase Calculator shows the Moon's phase name, illuminated fraction and upcoming phase milestones for any date you choose. Pick a date and read the whole dashboard at once — tonight's Moon explained, and the next full and new moons in view.
- 1Pick a date.
- 2Read phase and illumination.
What people use Moon Phase Calculator for
1. Tonight, at a glance
The single check before an evening out: what the Moon is, how bright, and whether it will help or hinder. Rise times live in Moonrise and Moonset when the plan needs hours too.
2. Planning a month of nights
Milestones — next full, next new — pace observing runs, photo projects and night events. The Moon Phase Calendar Map lays the same data out as a month grid.
3. Teaching the cycle end-to-end
One dashboard carries the whole story: age drives the name, the name matches the picture, the percent prices the light. Students who meet all four together stop memorising and start seeing.
4. Checking a claim about a date
Full moon at the wedding? Crescent for the crossing? The dashboard answers with the numbers exposed, not just the name — close calls show their margins.
Worked examples
Age 11.1 days is 75% of the way from new to full; the illumination formula turns that geometry into about 86% lit; the name for 'past quarter, not yet full, still growing' is waxing gibbous. Three readings, one Moon, zero contradictions.
Feed it 3 March 2026 and it reports full at ~100% — the night of a total lunar eclipse. Feed it 12 August 2026 and it reports new — a total solar eclipse. When a dashboard's extremes match the eclipse calendar, the middle values earn their keep.
The dashboard's four readings
What each number is and the tool that takes it further.
| Reading | Meaning | Deeper tool |
|---|---|---|
| Phase name | The cycle's chapter (new → full → new) | Moon Phase by Date |
| Age (days) | Time since the last new moon | Moon Age Calculator |
| Illumination | Lit fraction of the disc, percent | Moon Illumination Calculator |
| Milestones | Next quarter, full and new dates | Next Full Moon Calculator |
All readings derive from the mean synodic cycle (29.53059 days) — consistent with each other by construction, and within hours of the real sky's events in most cycles.
Moon phase is a global illumination geometry, while local visibility depends on location and time
The lunar phase describes the Sun-Earth-Moon geometry and can be estimated from the Moon's position in its synodic cycle. The same phase applies globally at a given moment, even though local clock dates can differ.
Actual visibility also depends on moonrise, moonset, weather, horizon obstruction and twilight. For scientific or observation planning that requires high precision, use an astronomical ephemeris rather than a simplified phase-cycle approximation.
How to interpret the result
The most common errors come from using a correct result to answer the wrong geographic question. Keep these points in mind for Moon Phase Calculator:
- When comparing day length across a year, remember the curve is your latitude's signature: near-equatorial sites hover at twelve hours while high latitudes swing wildly. Choose expectations by latitude, not by calendar folklore.
- Convert solar times to local clock times deliberately: the sun keeps astronomical time, while governments keep political time, and the gap between them is large in many countries. State both when sharing results.
Limits & appropriate use
Solar arithmetic's limits are small but real: the official zenith encodes average refraction, not today's atmosphere; coordinates are rounded to your input's precision; and terrain is absent unless you add height yourself — a mountain rises the sun late and the formulas won't know. Time adds the political layer: zones and DST are human law, and western edges of big zones (Spain, western China) make solar noon wander hours from clock noon. Every output here therefore carries its convention and both clocks, because an unanchored sunrise time is an argument, not a fact.
Lunar and seasonal outputs carry their own gentle limits: phase from the synodic approximation is hours-precise, which outruns every planning need but not ephemeris science; day length is geometric daylight, not sunshine, and clouds belong to climate's department. Escalation is rare and well-defined — astronomical almanacs and ephemerides for science, terrain-aware apps for mountain photography, and the tz database maintainers whenever a government invents a new DST rule at 48 hours' notice, as they delight in doing.
- Science-grade ephemerides → astronomical almanacs/JPL horizons.
- Mountain sunrise/sunset → terrain-aware horizon adjustments.
- Legal daylight definitions → jurisdictional statutes (they vary!).
Data & methodology
The workspace computes lunar phase and illumination from its local astronomy model for a chosen date; results are approximate and do not require a live astronomy service.
For source details, licences and model limitations, see Data Sources and Methodology.
Key terms worth knowing
- Civil twilight
- Sun between 0° and −6°: usable outdoor light without lamps.
- Synodic month
- The 29.53-day new-moon-to-new-moon cycle behind phases.
Editorial guidance: MapBench explains the method and limitations so the tool can be used as a transparent reference, not as a black-box answer. For legal boundaries, safety-critical routing, surveying, engineering, regulated decisions or official statistics, verify the result with the responsible authority or a qualified professional.
Category: Sun & Moon. Results are intended for everyday analysis and planning unless a page explicitly states otherwise.
Method, assumptions & limits
- This tool’s method
- The workspace computes lunar phase and illumination from its local astronomy model for a chosen date; results are approximate and do not require a live astronomy service.
- Before relying on the answer
- Check the date, location and time zone together. A solar or lunar event is tied to all three, and some events do not occur at high latitudes on a given date.
- What the result cannot establish
- A calculated event assumes the model's horizon and atmospheric conventions. Buildings, terrain and local weather can alter what you observe.
Coverage: Worldwide. Search, basemap and external data requests may use third-party services; browser-based does not mean every operation is offline. Read the source and licence notes, calculation methodology and privacy policy. If a result looks inconsistent, report a correction with the inputs and mode used.
Frequently asked questions
Clear answers about the calculation, accuracy and appropriate use.
Local time?
Phase is global; rise/set times depend on location — use moonrise tool for those.
Are sunrise and solar times exact to what I will see?
Calculated events use astronomical geometry. Terrain, buildings, weather and atmospheric conditions can shift what an observer actually sees.
Does daylight saving change the Sun's position?
No. Daylight saving changes the civil clock label, not solar geometry. Timezone rules affect displayed local time.
Why can polar locations show unusual results?
High latitudes can have days when the Sun does not rise or set, so some solar events legitimately do not occur on a selected date.
How accurate are the milestone dates?
Mean-model milestones land within several hours of the true instants in typical cycles — good for planning evenings, not for timing eclipse contacts. Almanacs and ephemerides own the last few hours.
Why do the name and the picture sometimes disagree?
Phase pictures are drawn for band centres; a Moon at a band edge wears its neighbour's face. The dashboard's age number is the tiebreaker — trust it over the icon.
Is the phase the same worldwide?
Essentially yes at any instant — the whole Earth shares one Moon geometry. The date line means the same Moon can carry two calendar dates at once, which is a calendar fact, not a lunar one.
What does 'gibbous' mean?
Humped — more than half lit, less than full, from the Latin for a hump. Waxing gibbous grows toward full; waning gibbous shrinks from it. The ugly word is the precise one.
Can it show the Moon for a historical date?
Yes — the cycle counts backward as happily as forward. Precision fades slowly over centuries, so a medieval date's phase name is a good estimate, not a sworn statement.
Why is the full moon sometimes a day off my calendar?
Printed calendars mark the date of the full instant in one timezone; the mean model can sit hours away, and your evening may precede the instant. Any of the three can move the label by a day near the boundary.
Does it include moonrise and set?
This dashboard is phase-first. The Moonrise and Moonset Calculator is the time-first sibling — the pair together cover a night completely.
What about eclipses and supermoons?
Eclipses need alignment precision beyond a phase model; supermoons need the Moon's distance, which this cycle doesn't track. The calculator names the phase honestly and leaves those events to ephemeris tools — while noting, correctly, that eclipses only ever occur at its two extreme readings.
Related tools and resources
Pieces of the dashboard: the Moon Age Calculator, Moon Illumination Calculator and Moon Phase by Date; times: Moonrise and Moonset.
More free tools
Sources, methodology & editorial trust
- ✓ Browser-first processing where supported
- ✓ External sources are documented
- ✓ No account required for public tools
- ✓ Review data sources
Calculations are documented with their assumptions, limitations and source context rather than presented as unexplained answers.
Reviewed and maintained by Aryan Khan, Founder & Editor of MapBench.
Part of our sun & moon hub
Moon Phase Calculator sits in the sun & moon cluster, alongside 27 other tools that answer neighbouring questions with different methods or datasets.
You may also need
When this answer is only part of the job, these clusters cover the next step.
Read the guide behind this tool
Full Moon Moonrise Times for 100 US Cities (2026–2027) — Moonrise time for every full moon, Oct 2026–Dec 2027, for America's 100 largest cities — including a Christmas Eve 2026 supermoon.