<form id="calc">
<select class="conv type" id="calc_conv_type">
<option data-unit="m">Длина</option>
<option data-unit="m2">Площадь</option>
<option data-unit="m3">Объём</option>
<option data-unit="kg">Вес</option>
<option data-unit="kg/m3">Плотность</option>
<option data-unit="h">Сила</option>
<option data-unit="pa">Давление</option>
<option data-unit="1/min">Частота</option>
<option data-unit="m/sec">Скорость</option>
<option data-unit="sec">Время</option>
</select>
<div id="calc_conv_content">
<div data-index="0">
<input type="number" min="0" id="calc_conv_0">
<span>м</span>
</div>
<div data-index="1">
<input type="number" min="0" id="calc_conv_1">
<span>мм</span>
</div>
<div data-index="2">
<input type="number" min="0" id="calc_conv_2">
<span>дюйм</span>
</div>
<div data-index="3">
<input type="number" min="0" id="calc_conv_3">
<span>фут</span>
</div>
<div class="reset">
<a class="vis">Очистить</a>
</div>
</div>
</form>