Gearing

glow dividing 48 by 18 won't get you the ratio

(chainring x 27*) / sprocket = ratio

*27 if you have 700c

Not exactly. If you have a 700C with a 28mm wide tyre, it's more like 26.7 (lower gear - easier to spin)

nimhbus yes it will.

48 divided by 18 is 2.6

the ratio is therefore 2.6:1

am i wrong?

It all depends on the size of the wheel/tyre combo.
A ratio of 2.6:1 with a 26" wheel is going to be easier to spin than the same ratio with a 700C x 28mm.

A couple of examples:
[ulist]
[li]26" x 1.5 @ 48:16 = (25 x 48) / 16 = 75 gear inches (tyre circumference is 25" despite being labelled as 26" nominal size)[/li]
[li]700C x 28mm @ 48:16 = (26.7 x 48) / 16 = 80 gear inches (tyre circumference is 26.7)[/li]
[li]700C x 20mm @ 48:16 = (26.1 x 48) / 16 = 78 gear inches (tyre circumference is 26.1)[/li]

[/ulist]