I don't understand the "search" comments.
Any subject on any forum comes up again and again and again....and again.
If I have something new to say on the subject, I welcome the opportunity.
If I don't have anything to say...I don't say anything.
I have ridden almost every possible gear inch combination from 59" to 82".
I have a bike intended for 54" on order.
Most factory fixies, like a Bianchi Pista or the like, come with 78".
I think experienced riders, on the average, settle down to 72".
Surprisingly, the 59" I now ride gives me the best round-trip times of any gear combo I have yet ridden.
When I rode 82" I could get to work (7.5 miles) in 23 minutes (three major stoplights).
Coming home, though, gaining 800', took me almost twice as long, 45 minutes.
Twenty-three plus 45 equals 68 minutes for a 15 mile round-trip, losing 800 feet one way and gaining it back coming home.
At 59" I take 30 minutes to get to work and 35 minutes to get home, for a total of 65 minutes.
Three minutes faster at 59".
Part of this gain might come from a more constant average speed.
Some of it comes from the increased acceleration at 59", which gives me a lot more capability/options at intersections and traffic circles; not to mention the increased control over deceleration at 59", which lets me hold more speed, longer, as I approach an intersection or traffic circle.
One also has to factor in my age, 61 years next week.
A younger rider would probably have the energy/wattage to make better use of the 82" gear combo than I do.
But then again, a younger rider might have a higher spin rate at 59" than do I.
Fun to think about.