iframe yüksekliğini stilden 355px verin.

Güncel kod :

<iframe frameborder="0" src="https://currencycalculate.com/tr/convertor/embed/" height="355" width="100%" sandbox="allow-same-origin allow-scripts allow-forms" scroll="no" style="overflow: hidden"></iframe>

Uygulamalı Örnekleri
https://bootsnipp.com/snippets/lVjg2