HTML input textbox with a width of 100% overflows table cells

Question

Does anyone know why the input elements with a width of 100% go over the table\'s cells border.

In the simple example below input box go over the table\'s cells border,

Answer 1

I know that this question is 3 years old but the problem still persists for current browsers and folks are still coming here. The solution for now is calc():

input {
    width: calc(100% - 12px); /* IE 9,10 , Chrome, Firefox */
    width: -webkit-calc(100% - 12px); /*For safari 6.0*/
}

It is supported by most modern browsers.