Moon Phase Software

Moon tools

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.

Earth and Moon distance diagram on an astronomy workbench

Geocentric output

Calculated Moon geometry

2026-09-20T19:21+00:00[UTC] · UTC

Earth–Moon center distance

402,416 km

29.68 arcminutes apparent diameter · 0.4947°

Libration longitude
−1.68°
Libration latitude
+4.43°
UTC instant

Reading the instrument

Four parts of the geometry

Every value uses Earth's centre as the reference point. That keeps the orbital measurement stable before any observer location is added.

01

Center distance

The straight-line distance between the centres of Earth and Moon.

02

Angular diameter

The modeled width of the lunar disc from Earth's centre; it generally grows as distance falls.

03

Sub-Earth libration

Longitude and latitude describing the apparent back-and-forth view of the lunar surface.

04

Perigee and apogee

Local distance minimum and maximum events searched on both sides of the selected instant.