How to Find the Moon Phase for Any Date

Enter a calendar date in YYYY-MM-DD format to get an estimated Moon phase, illumination, and lunar timing values. Leave the date blank to estimate the current date in UTC.

What the Moon Phase Calculator does

Use this tool to estimate the Moon’s phase and illumination for a calendar date. It is useful when you want a quick calendar-based view of whether the Moon is near a new moon, quarter, gibbous, or full moon phase. You can enter a date or leave the date field blank to use the current date in UTC.

The result is an estimate rather than an exact astronomical observation. Its calculation uses a synodic-month estimate anchored to a known new moon, not an ephemeris, so it does not provide location-specific or time-of-day astronomical calculations.

How to check the Moon phase for a date

1. Open the Moon Phase Calculator.
2. Decide whether you want a date-specific estimate or an estimate for the current UTC date. For a date-specific result, enter the date in YYYY-MM-DD format, such as 2025-04-15. If you leave the date blank, the tool uses the current date in UTC.
3. Submit the form using the available control.
4. Review the returned phase category, illuminated fraction, illumination percentage, estimated lunar-cycle age, and estimated time until the next new moon and full moon.

The date must follow the year-month-day format. A date that cannot be parsed produces a failed result, so check the order of the values and use a valid calendar date before submitting again.

How to read the result

The phase result uses one of eight categories: New Moon, Waxing Crescent, First Quarter, Waxing Gibbous, Full Moon, Waning Gibbous, Last Quarter, or Waning Crescent. “Waxing” indicates the illuminated portion is increasing in the cycle, while “waning” indicates it is decreasing.

Illumination appears as both a fraction and a percentage. The fraction is rounded to three decimal places, and the percentage is displayed to one decimal place. The timing values are estimates expressed in days, including the estimated lunar-cycle age and the estimated time until the next new moon and full moon.

Treat these values as calendar-date estimates. They should not be read as exact measurements or as a replacement for an ephemeris, especially when a location, time of day, or higher astronomical precision matters.

Worked example

You are planning a calendar entry for April 15, 2025 and want to review the Moon-phase estimate associated with that date.

Enter 2025-04-15 in the date field and submit it.

The returned result contains one of the eight phase categories, an illuminated fraction rounded to three decimal places, a percentage shown to one decimal place, estimated lunar-cycle age, and estimated days until the next new moon and full moon.

Limitations

• These are calendar-date estimates based on a synodic-month calculation, not ephemeris-grade measurements. The available calculation does not support location-specific or time-of-day results.

Common errors

• Entering a date in a format other than YYYY-MM-DD can cause the result to fail. Correct the order to year, month, and day, then submit a valid calendar date.

FAQ

What happens if I do not enter a date?

If you leave the date blank, the calculator uses the current date in UTC. To check another day, enter a valid date in YYYY-MM-DD format.

Which Moon phases can the calculator show?

The result assigns one of eight phase categories, from New Moon through Waxing Crescent, and includes estimated illumination values.

Are the Moon phase results exact astronomical measurements?

The calculator provides estimates based on a synodic-month calculation anchored to a known new moon. It is not an ephemeris and does not support location-specific or time-of-day astronomical calculations.

What timing information does the result include?

The result includes estimated lunar-cycle age and estimated time until the next new moon and full moon, expressed in days.