How tight should a fixie's chain be? I ride an SE Lager fixed.

How tight should the chain be and what is the best way of measure it? I have a chain tug so I can be pretty accurate in dialling in the right amount of tension.

I don't like to have much slop. Part of the joy of riding fixed is having a direct connection to the road. I like to have it adjusted so that there's no significant movement of the pedals when the bike is stationary. This often equates to about a centimeter of movement in the chain if I squeeze the top and bottom of the chain mid-way between the cog and chainring but it's hard to judge how hard I should be pushing to get that movement.

As always, Sheldon Brown has a lot of information, mostly about centering the chainring(!!) and recommends having the chain as tight as possible without binding.
The simple answer is, as Sheldon brown says, as tight as possible without binding. 
But define binding. The noises you described on your chain in your previous question were symptomatic of binding or of a worn chain. The description you've given there of how you run your chain tension is tighter than I would recommend. 


  To clarify the tensioning - When I replaced the chain I adjusted the tension. There was a very noticeable adjustment required. But then when I subsequently adjusted the rear cog I didn't adjust the tug from it's setting with the new chain. I agree that I might have changed the tension marginally just be removing and refitting the wheel.


1 millimeter of movement is too tight, in every case I've seen. The manufacturing tolerances on the components (cog, chain, and chain ring, ans well as the hub, and BB axle), would need absolute perfection to allow that tight of tension to function without damage or noise. I've never seen good enough all at once, and you would need to be amazingly lucky or diligent to find that mix of perfection.

Typical tension on a fixie or single speed is roughly 1/4" to 1/2", or 5-10 millimeters, when pressing on the chain from the top, and from one side. A single speed requires slightly less tension, because the bearings in the freewheel will bind, and it won't roll at all, where a fixie will just be noisy and prone to wear. Make sure you check for the spot where the chain is tightest, and do the adjustment there, as well.

You don't need to be that tight, and your drive train will still maintain good contact between pedal and wheel.