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Apparent vs Absolute Magnitude
What This Calculator Tells You
Apparent magnitude is how bright an object appears from Earth. Absolute magnitude is its intrinsic brightness - how bright it would appear from a standard distance of 10 parsecs (32.6 light-years). Use these calculators to convert between the two.
Calculate Absolute Magnitude
Given how bright an object appears and its distance, find its intrinsic brightness.
How bright the object appears from Earth.
1.43
Absolute Magnitude (M)
-2.89
Distance Modulus
2.64 pc
8.61 ly
Calculate Apparent Magnitude
Given an object's intrinsic brightness and distance, find how bright it appears.
Intrinsic brightness at 10 parsecs.
4.83
Apparent Magnitude (m)
+0.00
Distance Modulus
10.00 pc
32.62 ly
Example Stars
Click a star to load its values into either calculator.
| Star | Apparent (m) | Absolute (M) | Distance (pc) | Load |
|---|---|---|---|---|
| Sun | -26.74 | +4.83 | 4.85e-6 | |
| Sirius | -1.46 | +1.42 | 2.64 | |
| Canopus | -0.72 | -5.60 | 95.00 | |
| Alpha Centauri A | -0.01 | +4.38 | 1.34 | |
| Vega | +0.03 | +0.58 | 7.68 | |
| Rigel | +0.13 | -7.00 | 265.00 | |
| Betelgeuse | +0.50 | -5.85 | 186.00 | |
| Polaris | +1.98 | -3.64 | 133.00 |
Note: Rigel and Betelgeuse are intrinsically far brighter than Sirius, but appear dimmer because they're much farther away.
Understanding the Concepts
- Apparent magnitude (m): What we observe from Earth. Affected by both intrinsic brightness AND distance.
- Absolute magnitude (M): Standardized to 10 parsecs. Allows fair comparison of different stars' true luminosities.
- Distance modulus: The difference m - M. Positive means the object is farther than 10 pc; negative means closer.
- The Sun's absolute magnitude is +4.83: If placed 10 parsecs away, it would be a modest 5th magnitude star.
Rules of Thumb
- 5 magnitudes = 100x brightness: Each magnitude is about 2.512x difference
- Negative absolute magnitude = very luminous: Supergiants like Rigel have M around -7 to -8
- High absolute magnitude = dim intrinsically: Red dwarfs may have M around +10 to +15
- Double distance = +1.5 magnitudes dimmer: Brightness falls with square of distance
Related Calculators
- Limiting Magnitude Calculator - What's the faintest you can see?
- Surface Brightness Calculator - For extended objects