Doesn't matter. You can't go giving advice on gearing when you don't know the hill grade/fitness or weight of rider.

Now, making generalizations such as fixed gear bike can use slightly taller gearing I think is different.

So then you say practice on freewheel bike and determine ideal single ratio....then when you move to fixed gear increase ratio slightly. That's sounds like good advice.

But Pulling some gear ratio out of thin air.....come on.

P.S. Fixed gear plans for construction are underway. (fixed gear bike sounds more and more fun now that I think about all this stuff)

i ride 49x18 -- at a comfortable cadence you'll do about 18-21mph (~81-94 rpm), then if you're really hauling ass you can get up to 30mph (~134 rpm) without totally flying out of the saddle, although it isn't exactly sustainable. i will usually peak out on hills around 28-29mph, part of it though is just not wanting to crash into something. i'm planning on switching to 49x15 once my legs get a little stronger.

II know its different for everyone, but I think saying to stick between 68 & 75 gear inches on your first bike is fairly sound advice. Most people find that range to be pretty versatile and if anyone was saying that they were going to make their first S/S outside of that range, I would advise against it unless they had either major fitness or terrain issues to be taken in to account.

I wasn't trying to dictate a right answer, just trying to give some general guidelines.

77.3 or 50t x 17t for portland, or

does it matter if one's gearing comes from the front or the back? ie, is there a difference b/w say, 42/17 (71.5 gear inches) and 49/20 (70.9) beyond the slight change in gear inches?
also, what is the second wheel size number in Sheldon's gear inch calculator 700x20, 700x34, etc.
thx

a 71 inch gear is a 71 inch gear, regardless of the cog/ring combination you chose.
Though, larger cogs and chainrings will apparently last longer, by distributing wear over a larger area.
Also, some people think certain cog/ring combinations are better than others due to their relative number of "skid patches" (do a search), but meh.

the second number in the calculator is the "width" of the tire, which generally has a bearing on the hight of the tire's sidewall. Larger tires = taller gear, given the same chainring/cog combination.

What he said.

You could also throw in the idea that larger chainrings and cogs are more efficient than small chainrings and smaller cogs due to less bending of the chain links.

A 48-16 would be more efficient than a 36-12 for example. Maybe not a huge difference, but it is there.