First you need to know when it's started...i.e. when you start seeing trace level of ammonia...usually a couple of weeks depending on what you are using to cycle. Once the ammonia peeks it will convert to nitrite...so you should start seeing levels of that showing up. Nitrite with then convert to nitrate and then that will level off as well...maybe not completely depending on the water quality going into your tank. Your biological filter will always produce some amount of nitrate. Once everything has peaked and then dropped to 0 on your tests....your cycle is complete