 <p>Use django <code>F()</code> expression and <code>update()</code>:</p> <pre><code>from django.db.models import F Model.objects.filter(condition=condition).update(field=F('field') * 1.5)) </code></pre> <p>django doc about <a href="https://docs.djangoproject.com/en/1.9/ref/models/expressions/#f-expressions" rel="nofollow">F()</a> and <a href="https://docs.djangoproject.com/en/1.9/ref/models/querysets/#update" rel="nofollow">update</a>.</p> <p>PS: Your model names are not following python class conventions. The should be capfirst with no underscores in between. Check <a href="https://www.python.org/dev/peps/pep-0008/#class-names" rel="nofollow">pep8 doc</a> for python class naming details.</p>