Frequently Asked Questions
Everything you need to know about the Stellar Magnitude Calculator.
What is absolute magnitude?
A star's brightness as it would appear from a standard distance of 10 parsecs, allowing fair comparison between stars.
What is apparent magnitude?
How bright a star appears from Earth, which depends on both its true brightness and its distance.
How does this calculator work?
Enter any two of apparent magnitude, absolute magnitude, and distance, and it solves for the third using M = m − 5log₁₀(d) + 5.
Is it free?
Completely free, no sign-up, downloads, or limits.
Why is a lower magnitude brighter?
The magnitude scale is inverted and logarithmic — a historical convention — so smaller (even negative) numbers mean brighter objects.
Can I compare brightness between two stars?
Yes, use the brightness-ratio section: enter two magnitudes and see exactly how many times brighter one is.
Can I use light-years instead of parsecs?
Yes, there's a unit toggle for distance between parsecs and light-years.
What happens if I enter a distance of zero?
The calculator rejects it, since the logarithm is undefined at zero.
Is my data stored?
No; everything runs in your browser and isn't stored or sent anywhere.
Does it work on mobile?
Yes, fully responsive on all screen sizes.