input 100% with by Vladimir Starkov @matmuchrapna

HTML

<div class="input_wrap">
    <input type="text" />
</div>

CSS

/*
 * input 100% with by Vladimir Starkov @matmuchrapna
 */

div {
    padding: 6px 40px; /* equal to negative input's margin for mimic normal `div` box-sizing */

    /* demo only customizations */    
    background: red;
}

input {
    width: 100%; /* force to expand to container's width */ 
    padding: 5px 00px;
    border: none;
    margin: 0 -40px; /* negative margin = border-width + horizontal padding */ 
    
    /* demo only customizations */
    border-radius: 14px;
}