Absolute Magnitude Calculator

Enter any 2 values (apparent magnitude, stellar parallax, or absolute magnitude) into the Calculator. The calculator will evaluate the missing value. If you use parallax, make sure the selected unit (arcsec/mas/µas) matches your input.

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Absolute Magnitude Formula

The following example problem outlines the steps and information needed to calculate the Absolute Magnitude.

M = m + 5\left(\log_{10}(p_{\text{arcsec}}) + 1\right)

Variables:

• M is the Absolute Magnitude (mag)
• m is the apparent magnitude (mag)
• p is the stellar parallax in arcseconds (arcsec)
• If parallax is given in milliarcseconds (mas): M = m + 5\log₁₀(p_mas) – 10

How to Calculate Absolute Magnitude?

The following steps outline how to calculate the Absolute Magnitude.

1. First, determine the stellar parallax (make sure you know its units, such as arcsec or mas).
2. Next, determine the apparent magnitude.
3. Next, gather the formula from above: M = m + 5*(log₁₀(p_arcsec) + 1).
4. Finally, calculate the Absolute Magnitude.
5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

stellar parallax = 30 mas (0.03 arcsec)

apparent magnitude = 4

M = m + 5*(log₁₀(p_arcsec) + 1) = ?