Calculate the right sprocket-and-chainring tooth ratio for your bike with Affinity\'s gear ratio calculation chart. Whether you\'re racing on the track or flying through the streets, it\'s critical to have the right gear ratio for your needs or your daily route between work and home.Although online calculators are available, they are not 100% reliable. That\'s why Affinity has designed a durable and portable plastic gear ratio calculator to take home or to the velodrome to set up the perfect gear ratio for every situation.Simply rotate the wheel to the size of the crankset you have or will be using, between 47 and 65 teeth, and you will see the gear ratio based on the number of teeth on the sprocket, between 12 and 17, and the size of the tyre you are using. The calculations are based on 700c wheels with a total of 342 combinations indicated in metres and inches.