 <p><code>NSString</code> has an instance method <code>intValue</code> that might make this more straightforward.</p> <pre><code>NSNumber *value = [NSNumber numerWithInt:[[params objectAtIndex:i] intValue]]; </code></pre> <p>Now insert that <code>value</code> into the array. If the string is always this simple, you really don't a number formatter.</p>