'bar width sizes

.

To measure your current bar either go from outside edge on one side to inside edge on the other (this is same as c-to-c) or both outside edges for overall width.

If you like the ergonomics then get hold of a wider version of the same model. Or go to a shop and say "Can you get me a wider one of these?" Shouldn't be too difficult.

40's eh? What bars are they?

42 outside edge to outside edge will be a 40cm in *most* bars, which is relatively narrow. Like Jo says, some manufacturers measure the way you have so check when you're buying. Many bike fitters will advise you that the width between the bony bumps on the tops of your shoulders (the name of which i forget) is the centre-to-centre bar width you should choose, although for me that's 42cm and I prefer a 44.

some manufacturers measure their bars centre-to-centre, some outside edge to outside edge, which is pointlessly confusing, but it will usually say

probably best just to go the next width up if you feel cramped rather than go as big as possible

They are measured from centre of tube to centre of tube.