Kilograms to Pounds with select
HTML
<label> Weight:</label>
<input type="text" id="weight_value" />
<select id="weight_unit" />
<option value="lbs">lbs</option>
<option value="kg">kg</option>
</select>
JavaScript
var kg = 0.45359237
$(document).ready(function() {
$("#weight_unit").change(function() {
if ($(this).val() == "kg") {
$("#weight_value").val( $("#weight_value").val()*kg)
} else {
$("#weight_value").val( $("#weight_value").val()/kg)
}
});
});