 <p>Try this, this should work if any of the fields are empty.</p> <pre><code>if (temprature == 0 || methane == 0 || ethane == 0 || propane == 0 || nbutane == 0 || ibutane == 0 || oxygen == 0 || npetane == 0 || ipetane == 0 || nhexane == 0 || nitrogen == 0) { outputText.text = @"Please enter all values"; } else { outputText.text = resultString; } </code></pre>