I've seen formulas to calculate chain length for multi-speed bikes, but I need something for single speed.
Example: 42T Chainring 17T Cog 406mm (16") Chainstay Length
The answer in this case should come to ~94L.
Scroll to the bottom, equation is there, you want the "Rigorous Equation".
Better solution: start with heltonbiker's question on the math stack and ask how to convert to chain length.