要重现您的问题，我必须更改Chrome的缩放级别。将缩放级别更改回100％即可解决问题。它似乎是一个错误，计算的边框宽度总是小于定义的边框宽度，放大或缩小！

To reproduce your problem I have to change the zoom-level of Chrome. Changing the zoom-level back to 100% fixes it. It appears to be a bug, the calculated border width is always smaller than the defined border width, zooming in or out!

您的10px边框的值为10缩放级别是110％，但在125％它有与您的3px边框相同的问题。

Your 10px border does give a value of 10 when the zoom-level is 110%, but on 125% it has the same problem as your 3px border.

edit：firefox有相同的行为！

edit: firefox has the same behavior!