100% width on input tag

Hi when I add a rectangle and add this to inner html <input type="text" style="width:100%;"></input> then the input get’s wider than the rectangle, am I doing something wrong?

It looks like for a rectangle 100px wide, the ‘width’ computed value is set at 98px, but with borders and padding there is a little extra space added on either side and it gets to 101px (at least in Safari, this is likely different in other browsers). I recommend using 90% or something smaller: