JSFiddle - React, Tailwind, and code Playground

HTML

<div class="calculator">
    <div class="goup_param">
        <label>Ширина: <input type="text" class="form_price" name="width" id="width" value="" placeholder="0" /></label>
        <br />
        <br />
        <label>Высота: <input type="text" class="form_price" name="height" id="height" value="" placeholder="0" /></label>
        <br />
        <br />
        <label>Выбирите материал</label>
        <br />
        <select >
            <option value=""></option>
            <option value=""></option>
            <option value=""></option>
            <option value=""></option>
            <option value=""></option>
        </select>
    </div>
    <div>
      <button onclick="calculate()">Расчитать</button>
    </div>
    </div>
    <div class="total">
        <span id="fc_priceValue"></span> &#8381;
        <span id="fc_square" class="field">/ <span id="fc_squareValue">100</span> <span id="fc_squareMeas">м</span><sup>2</sup></span>
    </div>

JavaScript

function calculate(){
		var width = $('#width').val();
		var height = $('#height').val();
		var S =  width * height;
		var total = width * height * 2500;
		var newTotal = Math.round(total);	
		$('#fc_priceValue').html(newTotal);
}