What are the algorithms used for the calculator?

[NovaTitan]

For monitor match 0% based on the FOV of a game, what would be the algorithms/equations used for the calculator? I think it involves arctan, etc, but I could not find a thread from searching. I just want equations for say FOV 70 converting from FOV 106.26 or FOV 103. What are the numbers behind the calculator?

 

What values do I insert if I'm to figure it out?

[Drimzi]

circumferenceNew = circumferenceOld * ( tan(fovOld * pi/360) / tan(fovNew * pi/360) )

Edited September 28, 2018 by Drimzi

[NovaTitan]

Thank you, Drimzi. I will try this out for some indie titles like Goinund.

Edited September 28, 2018 by NovaTitan