Before finding the ratio of two inches to three inches, we must know what a ratio is. A ratio is a relationship between two numbers that have the same 'unit' (like inches). To find the ratio of 2 inches to 3 inches, we can just put a division sign or a colon instead of the 2 and cross out the inches since it is common. That means that the ratio of two inches to three inches is 2:3 or two thirds.