Free Inverse Square Brightness Calculator
Compare the brightness of an object at two different distances using the inverse square law: F2/F1 = (d1/d2)^2.
any
any
Brightness Ratio (F2/F1)
0.250000
Magnitude Difference1.5051 mag
Brightness Ratio (F2/F1) vs Distance 1
Inverse Square Law
Brightness (flux) decreases with the square of the distance from the source.
F2 / F1 = (d1 / d2)²
In magnitudes: m2 - m1 = 5 log10(d2 / d1)
Doubling the distance reduces brightness to 25% and increases magnitude by 1.505.
Example Calculation
Compare brightness at distances 1 and 2 (same units).
- 01F2/F1 = (1/2)² = 0.25
- 02At twice the distance, brightness is 25%.
- 03Magnitude diff = 5 log10(2) = 5 × 0.301 = 1.505 mag fainter.