코드 : 

function temp (form) {
  form.fahrenheit.value = form.celsius.value*1.8+32;
}

html :

<form>
<div align="center"><center><p><input type="text" size="15" name="celsius"> <strong>섭씨</strong> <input type="button" value=" = " onclick="temp(this.form)"> <input
Type="text" size="15" name="fahrenheit"> <strong>화씨</strong> </p>
</center></div>
</form>