Вы можете добиться того же, используя CSS и фон, тогда вам будет легко изменить размер:
.box {
width:100px;
height:100px;
display:inline-block;
background:
linear-gradient(gray,gray),
linear-gradient(gray,gray),
#B0b0b0;
background-size:100% 2px,2px 100%;
background-position:center;
background-repeat:no-repeat;
border:1px solid gray;
}
<div class="box">
</div>
<div class="box" style="width:200px;height:200px;">
</div>
С SVG вы можете рассмотреть процентное значение:
rect {
width: 50%;
height: 50%;
}
<svg style="width: 100px; height: 100px;" id="square">
<g>
<rect y="0" x="0" stroke-width="2" stroke="gray" fill="#B0b0b0"/>
<rect y="50%" x="50%" stroke-width="2" stroke="gray" fill="#B0b0b0"/>
<rect y="0" x="50%" stroke-width="2" stroke="gray" fill="#B0b0b0"/>
<rect y="50%" x="0" stroke-width="2" stroke="gray" fill="#B0b0b0"/>
</g>
</svg>
<svg style="width: 200px; height: 200px;" id="square">
<g>
<rect y="0" x="0" stroke-width="2" stroke="gray" fill="#B0b0b0"/>
<rect y="50%" x="50%" stroke-width="2" stroke="gray" fill="#B0b0b0"/>
<rect y="0" x="50%" stroke-width="2" stroke="gray" fill="#B0b0b0"/>
<rect y="50%" x="0" stroke-width="2" stroke="gray" fill="#B0b0b0"/>
</g>
</svg>