Moon Distance & Angular Size Explorer

Change the Earth-Moon distance to see how the same physical lunar diameter occupies a different angle in the sky.

Why apparent size changes

The Moon's orbit is elliptical. When it is closer, its fixed physical diameter subtends a larger angle; when farther away, it appears smaller. Popular labels such as “supermoon” describe combinations of phase and orbital distance, but the underlying geometry is simply angular size.

The calculation

Angular diameter is calculated as 2 × arctan(diameter ÷ 2 distance), using a mean lunar diameter of about 3,474.8 km. The range control is intentionally limited to representative Earth-Moon distances rather than implying an unlimited physical orbit.