HowTo? Fixed / Singlespeed conversion from an old bike

i've read all of sheldon brown but my maths is terrible. should i use my 50 or 36 tooth chainring for a single-speed conversion with a 16 tooth sprocket? i know around 42 is ideal but i cant afford a new chainring.

i'm not super fit so i'm drawn to the 36 but i also hate frustratingly low gear, obvs.

thoughts anyone?

well the 36 will give you 59 gear inches, and the 50 will give you 82 gear inches.

Neither of those is ideal but of the two i would go with the 36t chainring, i ride 63 gear inches, so 59 will be spinny but fine.