Moon Phase Software

Tools & method

Moon distance and apparent size for an exact time

Enter a local civil date, 24-hour time, and IANA time zone to calculate the center-to-center Earth–Moon distance, apparent angular diameter, sub-Earth libration, and the previous and next perigee and apogee.

Geometry input




Use a named IANA time zone so historical clock rules are applied. The default is UTC.

Calculated Moon geometry

Earth–Moon center distance
379,605 km
Apparent angular diameter
31.47 arcminutes (0.5245°)
Sub-Earth libration longitude
−4.75°
Sub-Earth libration latitude
−4.95°
Nearest apsis in time
Perigee, next ; 6 days, 11 hours, 59 minutes after the selected instant, at 368,249 km
Selected instant in UTC
2026-08-31T08:45+00:00[UTC]
UTC instant
Show previous and next perigee and apogee
Strictly adjacent lunar apsides around the selected instant
ApsisPrevious in UTCPrevious distanceNext in UTCNext distance
Perigee
UTC 10 Aug 2026, 11:18
363,273 km
UTC 6 Sept 2026, 20:44
368,249 km
Apogee
UTC 22 Aug 2026, 08:20
404,632 km
UTC 19 Sept 2026, 02:59
404,210 km

What the values mean

Geocentric distance
The distance between the centers of Earth and the Moon, not the distance from a person or a point on Earth's surface.
Angular diameter
The apparent width of the full lunar disk as seen from Earth's center. A smaller distance generally produces a larger angular diameter.
Sub-Earth libration
Longitude and latitude angles describing the Moon's apparent back-and-forth wobble relative to its mean Earth-facing position.
Perigee and apogee
The local minimum and maximum of the changing center-to-center Earth–Moon distance. The table brackets the selected instant with a strictly previous and strictly next event of each type.

Scope and limitations

Need the illuminated phase and adjacent new, quarter, and full Moon events instead? Use the exact-time Moon Phase Calculator. To include an observer location, use the Moon Position Calculator. Calculation definitions, validation fixtures, and model limits are documented in the distance calculation methods and sources.