CalculationTime

Moon Phase Calculator

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Moon Phase Calculator: Waxing Crescent · 3.7% lit. 2026-07-16 Astronomy Engine phase-age equivalent 1.81 days from lunar elongation. Next full moon from SearchMoonPhase(180) in 13.61 day(s); next new moon from SearchMoonPhase(0) in 27.73 day(s).

Formula applied

The exact method behind this answer

CalculationTime keeps the method visible so the number can be checked instead of blindly trusted.

MoonPhase(date) -> elongation. Phase-age equivalent = elongation / 360 × 29.530588853. Illumination fraction = (1 − cos(elongation)) ÷ 2. SearchMoonPhase(0/180) finds the next new/full phase instants.
  1. Apply the formulaMoonPhase(date) -> elongation. Phase-age equivalent = elongation / 360 × 29.530588853. Illumination fraction = (1 − cos(elongation)) ÷ 2. SearchMoonPhase(0/180) finds the next new/full phase instants.Waxing Crescent · 3.7% lit2026-07-16 Astronomy Engine phase-age equivalent 1.81 days from lunar elongation. Next full moon from SearchMoonPhase(180) in 13.61 day(s); next new moon from SearchMoonPhase(0) in 27.73 day(s).

Your live breakdown

Current inputs in the calculation

These values come from the controls above and update when the calculator changes.

Year
2,026
Month
7
Day
16

Resulting answer

Waxing Crescent · 3.7% lit

2026-07-16 Astronomy Engine phase-age equivalent 1.81 days from lunar elongation. Next full moon from SearchMoonPhase(180) in 13.61 day(s); next new moon from SearchMoonPhase(0) in 27.73 day(s).

Answer
Waxing Crescent · 3.7% lit
Live support
2026-07-16 Astronomy Engine phase-age equivalent 1.81 days from lunar elongation. Next full moon from SearchMoonPhase(180) in 13.61 day(s); next new moon from SearchMoonPhase(0) in 27.73 day(s).

Assumptions used

What this answer assumes

Best for learning and planning moon-phase context. Use official ephemerides for local visibility, libration, occultations or precision work.

  • Uses Astronomy Engine MoonPhase and SearchMoonPhase.
  • Good for educational phase context and transparent calculation checks.
  • Local viewing conditions, moonrise time and libration are not included.
  • Dates are evaluated at UTC midnight.

Master’s Tip

How to use the result well

Master’s Tip: phase and moonrise are different questions. A full moon can be below the horizon at a given local time.

Printable record

What belongs in the saved calculation

Save the inputs, result, formula, assumptions, page URL and date together so the calculation can be reviewed later.

Year
2,026
Month
7
Day
16

What-if check

Engine lunar elongation

Moon phase is calculated from Astronomy Engine lunar elongation, with SearchMoonPhase used for the next exact new and full phase instants.

CheckValueNote
phase age1.81 daysengine elongation equivalent
new moon gap27.73 daysSearchMoonPhase(0)
full moon gap13.61 daysSearchMoonPhase(180)
illumination3.7% litengine phase brightness

Visual proof

Result path

InputMethodAnswerWaxing Crescent · 3.7% lit

2026-07-16 Astronomy Engine phase-age equivalent 1.81 days from lunar elongation. Next full moon from SearchMoonPhase(180) in 13.61 day(s); next new moon from SearchMoonPhase(0) in 27.73 day(s).

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Explain it like I'm 12

The calculator samples Astronomy Engine lunar elongation for the selected UTC date, labels the phase band, calculates illuminated fraction and searches the next exact new/full phase instants.

Formula

MoonPhase(date) -> elongation. Phase-age equivalent = elongation / 360 × 29.530588853. Illumination fraction = (1 − cos(elongation)) ÷ 2. SearchMoonPhase(0/180) finds the next new/full phase instants.

Worked example

For the selected UTC date, read the Moon-Sun elongation from Astronomy Engine. Convert that angle to an equivalent phase age, calculate illumination from the cosine of the angle, then search the next 0° and 180° phase instants.

Professional note

Master’s Tip: phase and moonrise are different questions. A full moon can be below the horizon at a given local time.

Regional and unit assumptions

Standard or basis: Astronomy Engine lunar elongation at UTC midnight.

Assumptions and limitations

Methodology & Accuracy

How this calculator is checked

CalculationTime pages are built around visible arithmetic: the formula, assumptions, worked example and practical limitations are shown so the result can be checked rather than simply trusted.

Formula used

MoonPhase(date) -> elongation. Phase-age equivalent = elongation / 360 × 29.530588853. Illumination fraction = (1 − cos(elongation)) ÷ 2. SearchMoonPhase(0/180) finds the next new/full phase instants.

Standard or basis

Standard or basis: Astronomy Engine lunar elongation at UTC midnight.

Where a calculator follows a named legal, trade or industry standard, that standard is cited visibly. Otherwise the page uses transparent general arithmetic and states its limits.

Master's Tip

Master’s Tip: phase and moonrise are different questions. A full moon can be below the horizon at a given local time.

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Questions

What is lunar age?

Here it is an equivalent age derived from Astronomy Engine lunar elongation, useful for placing the Moon inside the familiar phase cycle.

Is illumination the same as visibility?

No. Illumination describes the lit fraction; weather, horizon, moonrise and local time affect visibility.

Is this an official ephemeris?

No. It is an engine-backed educational phase calculator, but local observing and professional ephemeris work still need source checks.

Calculation note

Moon phases follow the synodic month, the cycle from one new moon to the next.