This tool uses the impedance of the source and load to calculate the Reflection Coefficient (Γ) and Voltage Standing Wave Ratio (VSWR)
Source Impedance = Z0
Complex Load Impedance = R + j*X
Γ = √[(R-Z0)2 + X2] / √[(R+Z0)2 + X2]
VSWR = (1+Γ)/(1-Γ)
For a source impedance of 50 ohm and load impedance of 100 ohm, the reflection coefficient Γ = 0.33. The VSWR is 2.
Neither Γ nor VSWR have units as they are ratios.