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Planet Synodic Period Calculator

Time between successive same-configuration alignments.

Compute the synodic period S between two orbiting bodies (e.g. Earth and another planet) given their sidereal orbital periods T₁ and T₂, using 1/S = |1/T₁ − 1/T₂|.

Dr. Helena Ortiz By Dr. Helena Ortiz
Published Last reviewed 1 min read

Inputs

yr
yr

Results

Enter values and click Calculate to see results.
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How to use this calculator

  1. Fill in the inputs above using the units you already have.
  2. Values update automatically as you type — no submit button needed.
  3. Hover any result row for the underlying formula and intermediate values.

Formula

1/S = |1/T₁ − 1/T₂|

In depth

Compute the synodic period S between two orbiting bodies (e.g. Earth and another planet) given their sidereal orbital periods T₁ and T₂, using 1/S = |1/T₁ − 1/T₂|.