Apparent to Absolute Magnitude Converter

How it is calculated

The tool uses the distance modulus: μ = 5 × log₁₀(d) − 5 and M = m − μ, which is the same as M = m − 5 × log₁₀(d ÷ 10). Here m is the apparent magnitude as seen from Earth, d is the distance in parsecs and M is the absolute magnitude, the brightness the object would have at 10 parsecs. Magnitudes are unitless numbers on a scale where smaller or more negative means brighter. Results show two decimals. The distance must be above zero, while the apparent magnitude can be negative. Inside 10 parsecs the modulus is negative and the object is brighter than it would be at the standard distance. The formula ignores dust that dims starlight along the way.

Common mistakes

• Entering the distance in light-years. The field is parsecs, and one parsec is about 3.26 light-years, so divide light-years by 3.26 first.
• Entering the distance in kilometres or astronomical units. Both would give a nonsense result by many magnitudes.
• Getting the direction of brightness wrong. A lower magnitude means a brighter object, so an absolute magnitude of 1.43 is brighter than one of 5.
• Leaving out interstellar dust for distant stars. Extinction makes a star look fainter than its distance alone explains, so the absolute magnitude here comes out too faint.
• Mixing up the distance modulus with the absolute magnitude. The modulus is the difference m − M, shown as a second result; it is not the star's luminosity.