⭐Stellar Magnitude Calculator

Convert between apparent magnitude, absolute magnitude, and distance. Remember: on this scale, lower (even negative) numbers mean brighter, not dimmer.

Apparent magnitude (m)

Absolute magnitude (M)

Distance

Distance unit

Brightness Ratio Calculator

Compare two magnitudes to see how many times brighter one star is than the other, using the Pogson ratio.

Magnitude 1

Magnitude 2

Free Stellar Magnitude Calculator

Trying to work out how bright a star really is, not just how bright it looks from Earth? Our free Stellar Magnitude Calculator converts between apparent magnitude, absolute magnitude, and distance using the standard formula M = m − 5log₁₀(d) + 5. Enter any two values and the calculator solves for the third — with a toggle between parsecs and light-years for distance.

A built-in brightness-ratio tool also lets you compare two magnitudes directly, showing exactly how many times brighter one star is than another using the Pogson ratio — because on the magnitude scale, lower (even negative) numbers mean brighter, not dimmer.

Try the built-in presets for the Sun, Sirius, Betelgeuse, and Polaris to see real examples. No sign-up, no downloads, no limits. See the About page or the FAQ for more.