title: Bootstrap3 HTML set <label> length in a input-group
body: <p>I would like to make all the label having the same size as the img below:</p>
  
  <p><a href="https://i.stack.imgur.com/eUfGj.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/eUfGj.png" alt="labels on the form"></a></p>
  
  <p>This is the HTML snippet:</p>
  
  <pre><code>&lt;div class="form-inline"&gt;
      &lt;div class="col-xs-3 col-sm-3 input-group"&gt;
          &lt;span class="input-group-addon"&gt;&lt;label&gt;{{ form.area_construida.label }}&lt;/label&gt;&lt;/span&gt;
          &lt;input class="form-control" 
          id="id_{{ form.area_construida.name }}" 
          name="{{ form.area_construida.name }}" 
          value="{{ form.area_construida.value }}"                              
          type="text"/&gt;
      &lt;/div&gt;   
  &lt;/div&gt;   
  &lt;br&gt;
  &lt;div class="form-inline"&gt;   
      &lt;div class="col-xs-3 col-sm-3 input-group"&gt;
          &lt;span class="input-group-addon"&gt;&lt;label&gt;{{ form.area_total.label }}&lt;/label&gt;&lt;/span&gt;
          &lt;input class="form-control" 
          id="id_{{ form.area_total.name }}" 
          name="{{ form.area_total.name }}" 
          value="{{ form.area_total.value }}" 
          type="text"/&gt;
      &lt;/div&gt;
  &lt;/div&gt;
  &lt;br&gt;
  &lt;div class="form-inline"&gt;   
      &lt;div class="col-xs-3 col-sm-3 input-group"&gt;
          &lt;span class="input-group-addon"&gt;&lt;label&gt;Data de Construção&lt;/label&gt;&lt;/span&gt;
          &lt;input class="form-control"  data-validation="date" data-validation-format="yyyy-mm-dd"
          id="id_{{ form.data_construcao.name }}" 
          name="{{ form.data_construcao.name }}" 
          value="{{ form.data_construcao.value }}" 
          type="text"/&gt;
      &lt;/div&gt;
      &lt;p&gt;Insira o ano em que o imóvel foi construído&lt;/p&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>I tried some stuff but no success. Thanks.</p>