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Apparent Angular Size Calculator

Angular size of an object at a given distance.

Compute the apparent angular size (in degrees, arcminutes, and arcseconds) of an object of physical diameter D viewed from distance d, using θ = 2 · atan(D / 2d).

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

Inputs

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

θ = 2 · atan(D / (2 · d))

In depth

Compute the apparent angular size (in degrees, arcminutes, and arcseconds) of an object of physical diameter D viewed from distance d, using θ = 2 · atan(D / 2d).