what smiffy and the link are trying to tell you is that it is not *just* ratio you need to take into account.
it's a combination of chainstay length, chainring diameter/teeth, cog diameter/teeth and chainstretch/wear that is used to work it out.
We lack the required information to advise you with a single line answer, but you can work it out for yourself using the calculator in the link once you have the other bits of info.
Murray, thats a clever calculator but gives variants on the cs length not chain length
it shows both, the chainstay length is across the horizontal axis, the points plotted are colour coded to specific chain lengths. The vertical axis gives you the value of gear inches for the chosen options.
making some reasonable assumptions about your chainstay length if you are currently running 32x18, and with a new chain your *might* have some success with 33x19 or 35x21, others may work once chain worn slightly.
but both of those are going to be awkward to get rings for and I'm using assumptions, which is never a good thing
also - half link chains are easy and cheap to get online if none available locally and the extra weight is naff all really on the whole of the bike.