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Apparent magnitude (m) is brightness as observed from Earth. Each 5 magnitudes equals a 100× brightness factor. Vega is defined near m = 0; Sirius is −1.46.
Brightness ratio = 100^((m₁ − m₂) / 5)Distance modulus connects apparent and absolute magnitude. Absolute magnitude (M) is apparent magnitude at 10 parsecs (32.6 light-years).
m − M = 5 log₁₀(d/10 pc)Rearrange distance modulus to find absolute magnitude from apparent magnitude and distance, or compute apparent magnitude at any distance from known absolute magnitude.
M = m − 5 log₁₀(d/10)Updated: July 2026
Sun apparent magnitude −26.74 vs Moon −12.74. Difference of 14 magnitudes = 100^(14/5) ≈ 400,000× brightness ratio. The Sun is ~400,000 times brighter than the full Moon.
Betelgeuse apparent magnitude ~0.5 at 222 pc distance. Absolute magnitude M ≈ −5.5 — a red supergiant ~100,000× more luminous than the Sun.
Sun absolute magnitude 4.83. At 4.37 light-years (1.34 pc), apparent magnitude m ≈ 0.4 — similar to Capella, a bright star but not dominating the sky.
The magnitude scale is inverse — lower numbers are brighter. A star at magnitude 2 is brighter than one at magnitude 5, not dimmer.
A nearby dim star can appear brighter than a distant supergiant. Use absolute magnitude to compare true stellar luminosity across different distances.
Stellar magnitude scales measure brightness logarithmically, with apparent magnitude as seen from Earth and absolute magnitude at a standard 10 parsec distance. This calculator converts between them using distance to find true luminosity and brightness ratios.