Smaller dimensions = larger file?

[Mr Lucky]

When exporting to png, why would smaller dimensions cause a larger file size?

 

[John Rostron]

As far as I am aware, the compression algorithm used by png depends on the relative frequencies of sequences of bit patterns. This means that whilst, in general, a file with many pixels will have a bigger file size than one with fewer pixels, at the local level, there may be discrepancies such as you have observed.

John

[Pšenda]

... in general, the more pixels with the same color in the image, the better the compression (lossless) will be.

Just try to break up large areas with noise. The image will look more natural, but the file size will increase. And you may see the expected behavior (smaller dimensions = smaller file).