How do you work out how long your chain should be on a 1x9 set up? I've always used big ring/small sprocket and jockey wheels vertically inline for 3x9 set up, does this still apply?

A quick search on here found Park Tools answer:

SIMPLE EQUATION: L = 2 (C) + (F/4 + R/4 + 1)

L = Chain length in inches. Round the final result to closest whole inch figure.

C = Chain stay length in inches, measure to closest 1/8”. Use chart below to find decimal measurement.

F= Number of teeth on largest front chainring.

R= Number of teeth on largest rear cog.

Thoughts/advice appreciated