Why do I get a Format Exception when comparing int and float values?

I dont know why but I am getting a Format Exception when comparing two values. Could someone tell me what I am doing wrong? I already tried to make both values float, same exception... Sorry if its a stupid question, I m a noob, I know... Please help.

            float label1 = float.Parse(label15.Text);
            int box1 = int.Parse(label15.Text);

            if (label1 <= box1)
            {
            //Do things"
            }