css - How to make backgroud image of a button resonsive -

code use in jsp

<button class="refresh" onclick="javascript:regenimage();" type="button"></button> 

css use put image on button is

.refresh{     background-color: transparent;     background-image: url("../images/sp_out.png");     background-repeat: no-repeat;     height: 40px;     width: 43px; } 

by using image not getting responsive please me out

you need add

background-size: 100% auto; 

it means width of background 100% , height auto;

or can add this

 background-size: auto 100%; 

or

 background-size: 100% 100%;