Online Tool Store
Star Magnitude Brightness Comparator
Enter two stars' apparent magnitudes to see how many times brighter one is than the other, using the astronomical magnitude brightness ratio. Runs entirely in your browser.
🔒 This tool runs entirely in your browser. Your files are never uploaded to a server.
Example
Star Magnitude Brightness Comparator
Sample: Sirius (-1.46) vs. Polaris (1.98)
Example shown — replace it with your own two magnitudes.
Star A magnitude
-1.46 (Sirius)
Star B magnitude
1.98 (Polaris)
Result
How it works
- Enter the apparent magnitude of two stars.
- The magnitude difference is converted to a brightness ratio.
- See how many times brighter one star is than the other.
The method
Brightness ratio is calculated using the standard magnitude formula, where each magnitude step corresponds to a factor of about 2.512 in brightness.
FAQ
Why does a lower magnitude mean brighter?
The magnitude scale is inverted and logarithmic — it originated from ranking stars by eye, where the brightest stars got the lowest numbers, including negative values for the brightest objects.
What's the brightness ratio between magnitudes?
Each step of 1 magnitude corresponds to about a 2.512× brightness difference, so a 5-magnitude difference equals exactly 100× brightness.
Does this work for planets too?
Yes — apparent magnitude applies to any object viewed from Earth, including planets, not just stars.
How we compare
| Feature | Online Tool Store | Manual logarithm calculation | Astronomy textbook table |
|---|---|---|---|
| No software install | Yes | Yes | Yes |
| Quick to start | Yes | Slow | Search required |
| Free to use | Yes | Free | Free |
For a quick comparison without doing the logarithm math by hand, this gets you the ratio instantly.