Image resize often changes size

[dinz100001]

When I resize a photo wth or without interpolation or using the crop aspect tool, the size I create doesnt style exactly the same all of the time. Say I change the dimensions to 6inch on the long side, hats fine. But then when I check imafe properties it has changed to 5.993 inches. This is annoying as I want exact dimesnsions. Is this to do with some kind of math where the pixel dimensions and selected inches size can't evenly compute? 

[D Fosse]

It's important to understand that an image file doesn't actually have a "size". It's just pixels.

A physical size is determined by the pixels per inch-number, ppi. It means exactly what it says: how many pixels to stretch out over any given physical length measure. And the inverse: what ppi number distributes the available pixels over the required length.

In this case, your measurement doesn't add up to a whole number of pixels. You can't divide a pixel.

[dinz100001]

Thank you, still trying to get my head around this. So the only way to really get the size I want on the long edge is to love with what the resized image is? This is an issue when creating images with paper bleeds or printing borderless as instead of 6inch it's 5.998 so there's the possibility of white edges. Is the only option to make a slightly larger image to compensate for this? 

[D Fosse]

Thank you, still trying to get my head around this. 

By @dinz100001

Just say out loud, pixels per inch. Repeat it three times 😉

It really means just what it says, the whole thing right out in the open. There is no hidden meaning.

[dinz100001]

Why does PS allow me then to keep the values I enter  but then when I check the image it changes. Seems like there's no way to get exact proportions rhen? The only constant is PPI 

[dinz100001]

Thank you, still trying to get my head around this. So the only way to really get the size I want on the long edge is to love with what the resized image is? This is an issue when creating images with paper bleeds or printing borderless as instead of 6inch it's 5.998 so there's the possibility of white edges. Is the only option to make a slightly larger image to compensate for this?