Originally Posted by
Vixtor
Same chain length but different cog size will mess up your chain tension...two teeth = 2 links = an inch difference.
I'd definitely get a 15t to match your 16t a bit closer.
it's more like half an inch, since not all teeth of the cog and chainring are engaged at once. More or less half of the teeth in the cogs are engaged.
It might be possible to make a chain that fits both cogs by using a half link chain.