Confused about door latches

[pinksunsets]

So I think you have to measure from the centre of the handle to the edge of the door - is that right? That gives me around 5cm/2 inches but the shortest latch I can find is 2.5 inches. I'm confused!

They can be tricky to measure in situ. They're not difficult to remove and then you can get the size spot on. 2.5" is usually the shortest but there maybe some less common sizes in very old properties.