Sorry to do this, but you guys are like walking dictionaries and I don't quite understand the concept...

anyhow, I'm getting this Iro Crank: 130bcd with alloy 46 tooth ring, and I'm wondering what size cog to get.
I'm tall, I'm new to fixed gear, I'm going to be using a 170mm crank, and I live in ohio which is very very flat.

So what would you recommend? thanks.

I'd go with a 16 tooth. I thoroughly enjoy my 46x16 ratio and have since I started riding fixed.

16 or 15t.
Pretty standard gearing.

16

spinner or masher?

https://www.sheldonbrown.com/gears/

if you aren't a spinner already, become one. Your knees will thank you. Plus, if you decide to gear up, you'll be used to a higher cadence, which will make you spin faster anyway.

I run a 46x17. I think that it is near to perfect...although I guess I am a bit of a pansy judging by the previous responses. This is more or less 71 gear inches with either 165 or 170mm cranks.

Odd/even combos like the formentioned 46/17t will extend chain wear.

For me a gear in the mid-70's works well on both flat and hilly roads.

Why?

I rock a 45x17, which is like a 69.8 inch gear or thereabouts. I'm no pansy, I just spin faster.

uh what?

??? Is this a joke?

Get a T16, T15, T14, and T13.

Each one is a good jump on gear inches, each one serves a particular purpouse.

I change gears depending if I am commuting - (lower gearing for carrying loads) - or I am joyriding (for sheer speed). Even wind conditions will be a factor on what I would be gearing on a particular day.

It is like having a new bicycle every time. Save on shipping and buy those cogs.

End of Transmission

A combo that doesn't divide evenly will extend tire wear (more skid patches). However, both 46/16 and 46/17 give a lot of skid patches, so that's pretty much negligible.

I vote for the 16; I'm pushing a 48/16 and I'm no champ.

I prefer 48/16 to 48/15 too.

16 is a good combo with the 46. I ride that usually and it's a good all around gear.

Alright, thanks!
I ordered the 16 seeing as it seems to be the most popular. It's a starting point.

After all this work of putting the bike together and getting parts... I sure as hell better like fixed gear.

Around 70 gear inches works well for me. It's pretty fast on the flats, but not too tall for hills. I live in a illy area, but I'm not sure I would prefer taller gearing in a flat area. the ability to spin at a faster cadence is a good skill to build, and one of the reasons fixed gear bikes are so good for training. Before riding fixed I tended to ppick a tall gear, and "mash" to get my speed. Taking spinning classes, and riding fixed has improved my leg speed, ability to accelerate, as well as my ability to climb in tall gears.

well i know this is too late, but i think he shouldve trying getting as close as possible to the same gear inches as he mostly used on his geared bike, that's usualy a great start. i think anything from 68 -75 is a good start, but i think 70, 71, 72 are golden