Everybody gets this wrong and it’s not hard to see why. You look at a map, the scale says 1:1,000,000 and you think large number, large area covered - that must be large scale, right? Nope. Our brains like to associate big things with other big things, but brains like doing lots of things they probably shouldn't.
Large Scale vs. Small Scale Maps
The scale on a map is a representative fraction, so the scale of the map on the left a large scale map is 1:25,000 which means that objects on the map are drawn at 1/25,000 of their actual size.
The map on the right a small scale map is 1:4,500,000, so objects are 1/4,500,000 of their actual size. 1/25,000 is a larger fraction than 1/4,500,000 and a larger fraction means a larger scale! (If fractions aren't your thing just think of a pie cut into 25,000 slices, one of those slices is going to be much larger than a piece from a pie cut into 4,500,000 slices.)
Simple? No? An easy way to remember it is that the larger an object on the map is, the larger the scale is. So your brain can do its associations after all - it just has to do the right ones!